remove webRequest and webRequestBlocking

firefox was previously unable to use declarativeNetRequest, as some
browser state (ExtensionDNRStore) wasn't correctly initialized wrt
yomitan's use of the DNR API. this bug manifested as an unexpected
error on calls to updateDynamicRules(), specifically after the browser
has been restarted.

switching to the use of session rules instead of dynamic rules fixes
this bug. i have tested audio info requests (custom JSON, JPod
Alternate, Jisho) that exhibited the bug after browser restart on
version 115 and 118, and the audio plays instead of the request
failing.

webRequest can now be entirely removed.

dev/data/manifest-variants.json

@@ -248,31 +248,6 @@
                         "nativeMessaging"
                     ]
                 },
-                {
-                    "action": "add",
-                    "path": [
-                        "permissions"
-                    ],
-                    "items": [
-                        "webRequest"
-                    ]
-                },
-                {
-                    "action": "add",
-                    "path": [
-                        "permissions"
-                    ],
-                    "items": [
-                        "webRequestBlocking"
-                    ]
-                },
-                {
-                    "action": "remove",
-                    "path": [
-                        "permissions"
-                    ],
-                    "item": "declarativeNetRequest"
-                },
                 {
                     "action": "remove",
                     "path": [

docs/permissions.md

@@ -9,12 +9,7 @@
   `unlimitedStorage` is used to help prevent web browsers from unexpectedly
   deleting dictionary data.
 
-* `webRequest` and `webRequestBlocking` _(Firefox only)_ <br>
-  Yomichan uses these permissions to ensure certain requests have valid and secure headers.
-  This sometimes involves removing or changing the `Origin` request header,
-  as this can be used to fingerprint browser configuration.
-
-* `declarativeNetRequest` _(Chrome only)_ <br>
+* `declarativeNetRequest` <br>
   Yomichan uses this permission to ensure certain requests have valid and secure headers.
   This sometimes involves removing or changing the `Origin` request header,
   as this can be used to fingerprint browser configuration.