Remove a reference to the file AvoidCDataTextReaderTests.cs so that tarballs can be built again.
The file was removed in https://github.com/mono/mono/commit/d8d1b0be6baf6f8881871592b040d85be790926c
Merge pull request #1102 from tpokorra/TarballFixAvoidCDataTextReaderTests

Remove a reference to the file AvoidCDataTextReaderTests.cs so that tarballs can be built again