Updates the default branch from master to main (#16326)

* Updates the default branch from master to main

* Links from `master` to `main`

* Typo

* Update examples/flax/README.md

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

.github/workflows/model-templates.yml

@@ -3,7 +3,7 @@ name: Model templates runner
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
     paths:
       - "src/**"
@@ -60,7 +60,7 @@ jobs:
 
       - name: Run style changes
         run: |
-          git fetch origin master:master
+          git fetch origin main:main
           make style && make quality && make repo-consistency
 
       - name: Failure short reports