GHA: fork swift-testing for Android fixes

Pull the future main branch for Android fixes.

Author: compnerd

.github/workflows/swift-toolchain.yml

@@ -1893,11 +1893,19 @@ jobs:
           path: ${{ github.workspace }}/SourceCache/swift-corelibs-xctest
           show-progress: false
       - uses: actions/checkout@v4
+        if: matrix.os != 'Android'
         with:
           repository: swiftlang/swift-testing
           ref: ${{ inputs.swift_testing_revision }}
           path: ${{ github.workspace }}/SourceCache/swift-testing
           show-progress: false
+      - uses: actions/checkout@v4
+        if: matrix.os == 'Android'
+        with:
+          repository: swiftlang/swift-testing
+          ref: main-next
+          path: ${{ github.workspace }}/SourceCache/swift-testing
+          show-progress: false
 
       - run: |
           $RTLPath = cygpath -w ${{ github.workspace }}/BinaryCache/Library/Developer/Platforms/Windows.platform/Developer/SDKs/Windows.sdk/usr/bin