[meta] update references to master branch to main (#1619)

Author: aaronsky

.bazelci/update_workspace_to_deps_heads.sh

@@ -22,7 +22,7 @@ else
   INPLACE=("-i")
 fi
 
-# Modify the WORKSPACE to pull in the master branches of some deps.
+# Modify the WORKSPACE to pull in the main branches of some deps.
 sed \
   "${INPLACE[@]}" \
   -e \
@@ -39,7 +39,7 @@ git_repository(\
 git_repository(\
 \    name = "build_bazel_apple_support",\
 \    remote = "https://github.com/bazelbuild/apple_support.git",\
-\    branch = "master",\
+\    branch = "main",\
 )\
 ' \
   WORKSPACE

README.md

@@ -1,6 +1,6 @@
 # Swift Rules for [Bazel](https://bazel.build)
 
-[![Build status](https://badge.buildkite.com/d562b11425e192a8f6ba9c43715bc8364985bccf54e4b9194a.svg?branch=master)](https://buildkite.com/bazel/rules-swift-swift)
+[![Build status](https://badge.buildkite.com/d562b11425e192a8f6ba9c43715bc8364985bccf54e4b9194a.svg?branch=main)](https://buildkite.com/bazel/rules-swift-swift)
 
 This repository contains rules for [Bazel](https://bazel.build) that can be
 used to build Swift libraries, tests, and executables for macOS and Linux.
@@ -40,7 +40,7 @@ swift_library(
 
 ## Reference Documentation
 
-[Click here](https://github.com/bazelbuild/rules_swift/tree/master/doc)
+[Click here](https://github.com/bazelbuild/rules_swift/tree/main/doc)
 for the reference documentation for the rules and other definitions in this
 repository.