Fix error removing INPUT.MSG introduced in Commit d02fc1a2

remove() is expected to fail in this scenario sometimes depending
on how writemsg() is used - in the error case, the user was trying
to edit his .plan file with the ;plan command:
term Node 10 <Deuce> !ERROR 11 (Resource temporarily unavailable) in writemsg.cpp line 1232 (editfile) removing "/sbbs/node10/temp/INPUT.MSG" access=0

Thanks for the bug report!

src/sbbs3/writemsg.cpp

@@ -1228,8 +1228,7 @@ bool sbbs_t::editfile(char *fname, bool msg)
 
 		msg_tmp_fname(useron_xedit, msgtmp, sizeof(msgtmp));
 		if(stricmp(msgtmp,path)) {
-			if(removecase(msgtmp) != 0)
-				errormsg(WHERE, ERR_REMOVE, msgtmp, 0);
+			(void)removecase(msgtmp);
 			if(fexistcase(path))
 				CopyFile(path, msgtmp, /* failIfExists: */FALSE);
 		}