Various updates for renaming the master branch to main

.github/workflows/tests.yml

@@ -2,7 +2,7 @@ name: Tests
 
 on:
   push:
-    branches: [ 'master' ]
+    branches: ["main"]
   pull_request:
 
 concurrency:
@@ -33,7 +33,7 @@ jobs:
           path: dendrite
 
       # Attempt to check out the same branch of Complement as the PR. If it
-      # doesn't exist, fallback to master.
+      # doesn't exist, fallback to main.
       - name: Checkout complement
         shell: bash
         run: |
@@ -68,4 +68,4 @@ jobs:
         name: Run Complement Tests
         env:
           COMPLEMENT_BASE_IMAGE: complement-dendrite:latest
-        working-directory: complement
+        working-directory: complement