Switch references to master to main in the codebase + validating infra post-main migration (#44347)

* Update package.json

* Remove references to master in the codebase

* Add more master - main

.github/pull_request_template.md

@@ -3,12 +3,12 @@ Thank you for submitting a pull request!
 
 Please verify that:
 * [ ] There is an associated issue in the `Backlog` milestone (**required**)
-* [ ] Code is up-to-date with the `master` branch
+* [ ] Code is up-to-date with the `main` branch
 * [ ] You've successfully run `gulp runtests` locally
 * [ ] There are new or updated unit tests validating the change
 
 Refer to CONTRIBUTING.MD for more details.
-  https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md
+  https://github.com/Microsoft/TypeScript/blob/main/CONTRIBUTING.md
 -->
 
 Fixes #

.github/workflows/ci.yml

@@ -3,11 +3,11 @@ name: CI
 on:
   push:
     branches:
-      - master
+      - main
       - release-*
   pull_request:
     branches:
-      - master
+      - main
       - release-*
 
 jobs:

.github/workflows/sync-branch.yaml

@@ -28,8 +28,8 @@ jobs:
     - run: |
         git config user.email "typescriptbot@microsoft.com"
         git config user.name "TypeScript Bot"
-        git fetch origin master
-        git merge origin/master --no-ff
+        git fetch origin main
+        git merge origin/main --no-ff
         npm ci
         npm test
         git push