patch 8.2.4241: some type casts are redundant

Problem:    Some type casts are redundant.
Solution:   Remove the type casts. (closes #9643)
diff --git a/src/register.c b/src/register.c
index 03f7f4e..a3af8b3 100644
--- a/src/register.c
+++ b/src/register.c
@@ -1842,7 +1842,7 @@
 	    for (ptr = oldp; vcol < col && *ptr; )
 	    {
 		// Count a tab for what it's worth (if list mode not on)
-		incr = lbr_chartabsize_adv(oldp, &ptr, (colnr_T)vcol);
+		incr = lbr_chartabsize_adv(oldp, &ptr, vcol);
 		vcol += incr;
 	    }
 	    bd.textcol = (colnr_T)(ptr - oldp);