Connectivity repo now can use java_aconfig_library since this target is
available on all downstream branches.
This CL removes framework-connectivity-t-mdns-standalone-build-sources.
Files in this target use flags which won't be available in the
out-of-tree build but the next out-of-tree library import will not use
the classes in that filegroup anymore.
So the standalone build rule will still match the out-of-tree build.
Bug: 345121279
Test: TH
Change-Id: I2a9aa02bd0c9aa00d460f98cd51d5dec4098fb89
2fc115491a