Bump to xamarin/android-api-docs@5c4bf28f (#7099)

Changes: xamarin/android-api-docs@a7e9149...5c4bf28

  * xamarin/android-api-docs@5c4bf28f: Merge pull request #32 from xamarin/dabritch-config
  * xamarin/android-api-docs@4e096ef2: Master becomes main.
  * xamarin/android-api-docs@b1743ec3: Update docs using dotnet/java-interop@d3f0c5c

.gitmodules

@@ -1,7 +1,7 @@
 [submodule "external/android-api-docs"]
     path = external/android-api-docs
     url = https://github.com/xamarin/android-api-docs
-    branch = master
+    branch = main
 [submodule "external/apksig"]
     path = external/apksig
     url = https://android.googlesource.com/platform/tools/apksig