feat: Allowing shardCount to be nullified (#4437)

## Description
Allow shardCount to be nullified to disable default clustering behavior.

Below is the behavior of AVM before implementing the change to
shardCount.

<img width="1148" alt="Screenshot 2025-02-12 at 11 29 37 AM"
src="https://github.com/user-attachments/assets/6889136c-4473-4de3-9352-f763234f6430"
/>

After implementing the fix, the Premium cache is not clustered.

<img width="1151" alt="Screenshot 2025-02-12 at 11 28 56 AM"
src="https://github.com/user-attachments/assets/519f9de7-ece9-4d6e-ac39-4fbc551263dd"
/>

Fixes #4380 
Closes #4380 


## Pipeline Reference

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## Type of Change

<!-- Use the checkboxes [x] on the options that are relevant. -->

- [ ] Update to CI Environment or utilities (Non-module affecting
changes)
- [X] Azure Verified Module updates:
- [X] Bugfix containing backwards-compatible bug fixes, and I have NOT
bumped the MAJOR or MINOR version in `version.json`:
- [X] Someone has opened a bug report issue, and I have included "Closes
#{bug_report_issue_number}" in the PR description.
- [ ] The bug was found by the module author, and no one has opened an
issue to report it yet.
- [ ] Feature update backwards compatible feature updates, and I have
bumped the MINOR version in `version.json`.
- [ ] Breaking changes and I have bumped the MAJOR version in
`version.json`.
  - [ ] Update to documentation

## Checklist

- [X] I'm sure there are no other open Pull Requests for the same
update/change
- [X] I have run `Set-AVMModule` locally to generate the supporting
module files.
- [X] My corresponding pipelines / checks run clean and green without
any errors or warnings

<!-- Please keep up to date with the contribution guide at
https://aka.ms/avm/contribute/bicep -->

avm/res/cache/redis/README.md

@@ -2183,7 +2183,6 @@ The number of shards to be created on a Premium Cluster Cache.
 
 - Required: No
 - Type: int
-- Default: `1`
 - MinValue: 1
 
 ### Parameter: `skuName`

avm/res/cache/redis/linked-servers/main.json

@@ -5,8 +5,8 @@
   "metadata": {
     "_generator": {
       "name": "bicep",
-      "version": "0.33.13.18514",
-      "templateHash": "11294861621866290910"
+      "version": "0.33.93.31351",
+      "templateHash": "322534394383651316"
     },
     "name": "Redis Cache Linked Servers",
     "description": "This module connects a primary and secondary Redis Cache together for geo-replication."

avm/res/cache/redis/main.bicep

@@ -64,7 +64,7 @@ param replicasPerPrimary int = 3
 
 @minValue(1)
 @description('Optional. The number of shards to be created on a Premium Cluster Cache.')
-param shardCount int = 1
+param shardCount int?
 
 @allowed([
   0

avm/res/cache/redis/main.json

@@ -5,8 +5,8 @@
   "metadata": {
     "_generator": {
       "name": "bicep",
-      "version": "0.33.13.18514",
-      "templateHash": "1242857667100916577"
+      "version": "0.33.93.31351",
+      "templateHash": "2636464673565813214"
     },
     "name": "Redis Cache",
     "description": "This module deploys a Redis Cache."
@@ -842,7 +842,7 @@
     },
     "shardCount": {
       "type": "int",
-      "defaultValue": 1,
+      "nullable": true,
       "minValue": 1,
       "metadata": {
         "description": "Optional. The number of shards to be created on a Premium Cluster Cache."
@@ -1947,8 +1947,8 @@
           "metadata": {
             "_generator": {
               "name": "bicep",
-              "version": "0.33.13.18514",
-              "templateHash": "11294861621866290910"
+              "version": "0.33.93.31351",
+              "templateHash": "322534394383651316"
             },
             "name": "Redis Cache Linked Servers",
             "description": "This module connects a primary and secondary Redis Cache together for geo-replication."
@@ -2073,8 +2073,8 @@
           "metadata": {
             "_generator": {
               "name": "bicep",
-              "version": "0.33.13.18514",
-              "templateHash": "14045530027687796477"
+              "version": "0.33.93.31351",
+              "templateHash": "8063348652715653257"
             }
           },
           "definitions": {