Fix memory leak in pg_restore with zstd-compressed data.

EndCompressorZstd() neglected to free everything.  This was
most visible with a lot of large objects in the dump.

Per report from Tomasz Szypowski.  Back-patch to v16
where this code came in.

Discussion: https://postgr.es/m/DU0PR04MB94193D038A128EF989F922D199042@DU0PR04MB9419.eurprd04.prod.outlook.com

src/bin/pg_dump/compress_zstd.c

@@ -137,9 +137,10 @@ EndCompressorZstd(ArchiveHandle *AH, CompressorState *cs)
 		Assert(zstdcs->dstream == NULL);
 		_ZstdWriteCommon(AH, cs, true);
 		ZSTD_freeCStream(zstdcs->cstream);
-		pg_free(zstdcs->output.dst);
 	}
 
+	/* output buffer may be allocated in either mode */
+	pg_free(zstdcs->output.dst);
 	pg_free(zstdcs);
 }