lib/zlib/GzipOutputStream: rename Flush() to Finish()

src/lib/zlib/GzipOutputStream.cxx

@@ -55,7 +55,7 @@ GzipOutputStream::~GzipOutputStream()
 }
 
 void
-GzipOutputStream::Flush()
+GzipOutputStream::Finish()
 {
 	/* no more input */
 	z.next_in = nullptr;

src/lib/zlib/GzipOutputStream.hxx

@@ -56,7 +56,7 @@ public:
 	 * Finish the file and write all data remaining in zlib's
 	 * output buffer.
 	 */
-	void Flush();
+	void Finish();
 
 	/* virtual methods from class OutputStream */
 	void Write(const void *data, size_t size) override;