make: Fix the "clean" target to remove *.html in pgproto/codecs

Author: 1st1

Makefile

@@ -11,7 +11,7 @@ all: compile
 clean:
 	rm -fr dist/ doc/_build/
 	rm -fr asyncpg/pgproto/*.c asyncpg/pgproto/*.html
-	rm -fr asyncpg/pgproto/pgproto/*.html
+	rm -fr asyncpg/pgproto/codecs/*.html
 	rm -fr asyncpg/protocol/*.c asyncpg/protocol/*.html
 	rm -fr asyncpg/protocol/*.so build *.egg-info
 	rm -fr asyncpg/protocol/codecs/*.html