cut legacy backcompat alias folly::io::getAutoUncompressionCodec

Summary: All uses have been migrated so the unused alias may now be removed.

Reviewed By: skrueger

Differential Revision: D68544604

fbshipit-source-id: f2e08d87c01ead309ad0e64244deddb8ff7c9a58

Author: yfeldblum

folly/compression/Compression.h

@@ -543,7 +543,6 @@ bool hasStreamCodec(CodecType type);
 namespace folly::io {
 using folly::compression::Codec;
 using folly::compression::CodecType;
-using folly::compression::getAutoUncompressionCodec;
 using folly::compression::getCodec;
 using folly::compression::hasCodec;
 } // namespace folly::io