chore: remove references to master branch

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,7 @@
 Checklist:
 
 * [ ] I have updated the necessary documentation
-* [ ] I have signed off all my commits as required by [DCO](https://github.com/procore-oss/blueprinter/blob/main/CONTRIBUTING.md)
+* [ ] I have signed off all my commits as required by [DCO](https://github.com/procore-oss/ruby-sdk/blob/main/CONTRIBUTING.md)
 * [ ] My build is green
 
 <!--

.github/workflows/release.yaml

@@ -3,7 +3,7 @@ on:
   workflow_run:
     workflows: [Test]
     types: [completed]
-    branches: [master, main]
+    branches: [main]
   workflow_dispatch: # allow manual deployment through GitHub Action UI
 jobs:
   release:

.github/workflows/test.yaml

@@ -1,9 +1,9 @@
 name: Test
 on:
   push:
-    branches: [master, main]
+    branches: [main]
   pull_request:
-    branches: [master, main]
+    branches: [main]
 permissions:
   contents: read
 jobs:

README.md

@@ -563,7 +563,7 @@ Please **do not** bump the gem version in your PR. This will be done in a follow
 
 Gem maintainer should follow these steps to release a new version:
 
-1. Merge all PRs into the `master` branch that you want included in the release.
+1. Merge all PRs into the `main` branch that you want included in the release.
 2. Update `version.rb` to a new semantic version, and move unreleased items in `CHANGELOG.md` into a section for that version.
 3. Stage and commit changes. `git commit -a`
 4. Create a tag for the new version. `git tag -a {version}`