chore: change branch master to main in github configurations (#628)

Author: Neenu1995

.github/blunderbuss.yml

@@ -1,5 +1,5 @@
 # Configuration for the Blunderbuss GitHub app. For more info see
-# https://github.com/googleapis/repo-automation-bots/tree/master/packages/blunderbuss
+# https://github.com/googleapis/repo-automation-bots/tree/main/packages/blunderbuss
 assign_issues:
   - thiagotnunes
 assign_prs_by:

.github/sync-repo-settings.yaml

@@ -11,11 +11,11 @@ squashMergeAllowed: true
 # Defaults to `false`
 mergeCommitAllowed: false
 
-# Rules for master branch protection
+# Rules for main branch protection
 branchProtectionRules:
 # Identifies the protection rule pattern. Name of the branch to be protected.
-# Defaults to `master`
-- pattern: master
+# Defaults to `main`
+- pattern: main
   # Can admins overwrite branch protection.
   # Defaults to `true`
   isAdminEnforced: true
@@ -39,7 +39,7 @@ branchProtectionRules:
     - "cla/google"
 
 # Identifies the protection rule pattern. Name of the branch to be protected.
-# Defaults to `master`
+# Defaults to `main`
 - pattern: 1.21.x
   # Can admins overwrite branch protection.
   # Defaults to `true`

.github/workflows/integration-tests-against-emulator.yaml

@@ -1,7 +1,7 @@
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
 name: Integration tests against emulator
 jobs:

README.md

@@ -236,10 +236,10 @@ Java is a registered trademark of Oracle and/or its affiliates.
 [developer-console]: https://console.developers.google.com/
 [create-project]: https://cloud.google.com/resource-manager/docs/creating-managing-projects
 [cloud-sdk]: https://cloud.google.com/sdk/
-[troubleshooting]: https://github.com/googleapis/google-cloud-common/blob/master/troubleshooting/readme.md#troubleshooting
-[contributing]: https://github.com/googleapis/java-spanner-jdbc/blob/master/CONTRIBUTING.md
-[code-of-conduct]: https://github.com/googleapis/java-spanner-jdbc/blob/master/CODE_OF_CONDUCT.md#contributor-code-of-conduct
-[license]: https://github.com/googleapis/java-spanner-jdbc/blob/master/LICENSE
+[troubleshooting]: https://github.com/googleapis/google-cloud-common/blob/main/troubleshooting/readme.md#troubleshooting
+[contributing]: https://github.com/googleapis/java-spanner-jdbc/blob/main/CONTRIBUTING.md
+[code-of-conduct]: https://github.com/googleapis/java-spanner-jdbc/blob/main/CODE_OF_CONDUCT.md#contributor-code-of-conduct
+[license]: https://github.com/googleapis/java-spanner-jdbc/blob/main/LICENSE
 
 
 [libraries-bom]: https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/The-Google-Cloud-Platform-Libraries-BOM