Rename default branch to main

I've removed the `workflow_dispatch` trigger from `update-changelog.yaml` as the `workflow_dispatch` event does not have the release details in its payload so I doubt this would run successfully.

.github/workflows/update-changelog.yaml

@@ -1,11 +1,10 @@
 # This workflow takes the GitHub release notes an updates the changelog on the
-# master branch with the body of the release notes, thereby keeping a log in
+# main branch with the body of the release notes, thereby keeping a log in
 # the git repo of the changes.
 
 name: "Update Changelog"
 
 on:
-  workflow_dispatch:
   release:
     types: [released]
 
@@ -17,7 +16,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
         with:
-          ref: master
+          ref: main
 
       - name: Update Changelog
         uses: stefanzweifel/changelog-updater-action@v1
@@ -29,6 +28,6 @@ jobs:
       - name: Commit updated CHANGELOG
         uses: stefanzweifel/git-auto-commit-action@v4
         with:
-          branch: master
+          branch: main
           commit_message: Update CHANGELOG
           file_pattern: CHANGES.md

RELEASING.md

@@ -2,10 +2,10 @@
 
 To make a new release of pytest-mpl follow the following steps:
 
-* Ensure the sdist and wheel GitHub Actions jobs succeeded on master after the last merge.
+* Ensure the sdist and wheel GitHub Actions jobs succeeded on main after the last merge.
 * Also ensure that the tarball built has an autogenerated version number from setuptools_scm.
 * Write the release notes in the GitHub releases UI, use the autogenerated
   notes and tidy up a little.
 * Publish the new release, using the format `vX.Y.X`.
-* Watch as GitHub actions builds the sdist and universal wheel and pushes them to PyPI for you, and updates CHANGES.md on the master branch.
+* Watch as GitHub actions builds the sdist and universal wheel and pushes them to PyPI for you, and updates CHANGES.md on the main branch.
 * Enjoy the beverage of your choosing 🍻.