feat: remove unused push notification environment variables (#13270)

## **Description**

These variables are never used, and our FCM setup relies instead on the
B64 environment variables that you can generate in the README or
available through OnePassword.

## **Related issues**

## **Manual testing steps**

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->

### **After**

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## **Pre-merge author checklist**

- [x] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

.android.env.example

@@ -2,15 +2,3 @@ export MM_FOX_CODE="EXAMPLE_FOX_CODE"
 export MM_BRANCH_KEY_TEST=
 export MM_BRANCH_KEY_LIVE=
 export METAMASK_BUILD_TYPE=
-# Firebase
-export FCM_CONFIG_API_KEY=
-export FCM_CONFIG_AUTH_DOMAIN=
-export FCM_CONFIG_PROJECT_ID=
-export FCM_CONFIG_STORAGE_BUCKET=
-export FCM_CONFIG_MESSAGING_SENDER_ID=
-export FCM_CONFIG_APP_ID=
-export GOOGLE_SERVICES_B64_ANDROID=
-#Notifications Feature Announcements
-export FEATURES_ANNOUNCEMENTS_ACCESS_TOKEN=
-export FEATURES_ANNOUNCEMENTS_SPACE_ID=
-

.ios.env.example

@@ -1,14 +1,3 @@
 MM_FOX_CODE = EXAMPLE_FOX_CODE
 MM_BRANCH_KEY_TEST =
 MM_BRANCH_KEY_LIVE =
-# Firebase
-FCM_CONFIG_API_KEY=
-FCM_CONFIG_AUTH_DOMAIN=
-FCM_CONFIG_PROJECT_ID=
-FCM_CONFIG_STORAGE_BUCKET=
-FCM_CONFIG_MESSAGING_SENDER_ID=
-FCM_CONFIG_APP_ID=
-GOOGLE_SERVICES_B64_IOS=
-#Notifications Feature Announcements
-FEATURES_ANNOUNCEMENTS_ACCESS_TOKEN=
-FEATURES_ANNOUNCEMENTS_SPACE_ID=

.js.env.example

@@ -79,12 +79,6 @@ export PORTFOLIO_VIEW="true"
 # Temporary mechanism to enable security alerts API prior to release.
 export MM_SECURITY_ALERTS_API_ENABLED="true"
 # Firebase
-export FCM_CONFIG_API_KEY=""
-export FCM_CONFIG_AUTH_DOMAIN=""
-export FCM_CONFIG_PROJECT_ID=""
-export FCM_CONFIG_STORAGE_BUCKET=""
-export FCM_CONFIG_MESSAGING_SENDER_ID=""
-export FCM_CONFIG_APP_ID=""
 export GOOGLE_SERVICES_B64_ANDROID=""
 export GOOGLE_SERVICES_B64_IOS=""
 # Notifications Feature Announcements