patch 8.2.2828: Coverity complains about not checking rename() return value

Problem:    Coverity complains about not checking the rename() return value.
Solution:   Add "(void)", can't do anything in case of a failure.
diff --git a/src/fileio.c b/src/fileio.c
index 1af0b4c..b59c01d 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -3733,7 +3733,7 @@
 			return 0;
 		    // Strange, the second step failed.  Try moving the
 		    // file back and return failure.
-		    mch_rename(tempname, (char *)from);
+		    (void)mch_rename(tempname, (char *)from);
 		    return -1;
 		}
 		// If it fails for one temp name it will most likely fail