Fix error message.

Remove extra space.  Back-patch to all releases, like commit 7897e3bb.

Author: Lu, Chenyang <lucy.fnst@cn.fujitsu.com>
Discussion: https://postgr.es/m/795d03c6129844d3803e7eea48f5af0d%40G08CNEXMBPEKD04.g08.fujitsu.local

src/backend/storage/file/buffile.c

@@ -499,7 +499,7 @@ BufFileDumpBuffer(BufFile *file)
 		if (bytestowrite <= 0)
 			ereport(ERROR,
 					(errcode_for_file_access(),
-					 errmsg("could not write to file \"%s\" : %m",
+					 errmsg("could not write to file \"%s\": %m",
 							FilePathName(thisfile))));
 		file->curOffset += bytestowrite;
 		wpos += bytestowrite;