Update extended_install.md

Originally there was a Syntax Error in the "To trust the CRS project's public key:" section, where the command `gpg --edit-key` was misspelled as `gpg edit-key`. We fixed this by making the final syntax `gpg --edit-key`. 

Before:
----------------------------------------
```bash
gpg edit-key 
----------------------------------------

After:
----------------------------------------
changed to:
```bash
gpg --edit-key
---------------------------------------

content/deployment/extended_install.md

@@ -150,7 +150,7 @@ If the signature was good then the verification succeeds. If a warning is displa
 To trust the CRS project's public key:
 
 ```bash
-gpg edit-key 36006F0E0BA167832158821138EEACA1AB8A6E72
+gpg --edit-key 36006F0E0BA167832158821138EEACA1AB8A6E72
 gpg> trust
 Your decision: 5 (ultimate trust)
 Are you sure: Yes
@@ -234,4 +234,4 @@ Nginx will include files from the Nginx configuration directory (`/etc/nginx` or
 
 {{% notice note %}}
 You will also need to include the plugins you want along with your CRS installation.
-{{% /notice %}}
+{{% /notice %}}