Fix warnings: ex_getln.c: getexmodeline(): HI.

Problem    : Dead increment @ 1795.
Diagnostic : Harmless issue.
Rationale  : Line was necessary before (indent was used by the following
             while loop), but now that loop is removed, assignment is
             indeed dead.
Resolution : Remove line.

src/nvim/ex_getln.c

@@ -1792,7 +1792,6 @@ getexmodeline (
         p[line_ga.ga_len] = NUL;
         indent = get_indent_str(p, 8, FALSE);
         num_spaces = sw - indent % sw;
-        indent += num_spaces;
 add_indent:
         if (num_spaces > 0) {
           ga_grow(&line_ga, num_spaces + 1);