Add missing return type to read (#3707)

stdlib/3/_compression.pyi

@@ -11,6 +11,6 @@ class DecompressReader(io.RawIOBase):
     def close(self): ...
     def seekable(self): ...
     def readinto(self, b): ...
-    def read(self, size: int = ...): ...
+    def read(self, size: int = ...) -> bytes: ...
     def seek(self, offset, whence=...): ...
     def tell(self): ...