chore(deps): update dependency firebase/firebase-ios-sdk to from: "10.21.0" (#904)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[firebase/firebase-ios-sdk](https://togithub.com/firebase/firebase-ios-sdk)
| minor | `from: "10.20.0"` -> `from: "10.21.0"` |

---

### Release Notes

<details>
<summary>firebase/firebase-ios-sdk (firebase/firebase-ios-sdk)</summary>

###
[`v10.21.0`](https://togithub.com/firebase/firebase-ios-sdk/releases/tag/10.21.0):
Firebase Apple 10.21.0

[Compare
Source](https://togithub.com/firebase/firebase-ios-sdk/compare/10.20.0...10.21.0)

The Firebase Apple SDK (10.21.0) is now available. For more details, see
the [Firebase Apple SDK release
notes.](https://firebase.google.com/support/release-notes/ios#10.21.0)

To install this SDK, see [Add Firebase to your
project.](https://firebase.google.com/docs/ios/setup)

</details>

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examples/firebase_example/MODULE.bazel.lock

@@ -5,7 +5,7 @@ import PackageDescription
 let package = Package(
     name: "firebase_example",
     dependencies: [
-        .package(url: "https://github.com/firebase/firebase-ios-sdk", .upToNextMajor(from: "10.20.0")),
+        .package(url: "https://github.com/firebase/firebase-ios-sdk", .upToNextMajor(from: "10.21.0")),
         // Used by crashlytics example
         .package(url: "https://github.com/ashleymills/Reachability.swift.git", .upToNextMajor(from: "5.2.0")),
     ]

examples/firebase_example/Package.resolved

@@ -1665,9 +1665,9 @@
       "name": "swiftpkg_firebase_ios_sdk",
       "identity": "firebase-ios-sdk",
       "remote": {
-        "commit": "b880ec8ec927a838c51c12862c6222c30d7097d7",
+        "commit": "f91c8167141d0279726c6f6d9d4a47c026785cbc",
         "remote": "https://github.com/firebase/firebase-ios-sdk",
-        "version": "10.20.0"
+        "version": "10.21.0"
       },
       "cLanguageStandard": "c99",
       "cxxLanguageStandard": "gnu++14"
@@ -1676,9 +1676,9 @@
       "name": "swiftpkg_googleappmeasurement",
       "identity": "googleappmeasurement",
       "remote": {
-        "commit": "ceec9f28dea12b7cf3dabf18b5ed7621c88fd4aa",
+        "commit": "cb8617fab75d181270a1d8f763f26b15c73e2e1e",
         "remote": "https://github.com/google/GoogleAppMeasurement.git",
-        "version": "10.20.0"
+        "version": "10.21.0"
       },
       "cLanguageStandard": "c99",
       "cxxLanguageStandard": "gnu++14"