[iOS] Fix fade truncating label memory release

This CL releases frame_setter at the end of the call.

Bug: 1419861
Change-Id: I32be11a6d2b5cea6cafca2881087c0f6dcd21114
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4295424
Reviewed-by: Mark Cogan <marq@chromium.org>
Auto-Submit: Christian Xu <christianxu@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1110939}

ios/chrome/browser/ui/elements/fade_truncating_label.mm

@@ -83,6 +83,7 @@
     NSRange range = NSMakeRange(line_range.location, line_range.length);
     [line_ranges addObject:[NSValue valueWithRange:range]];
   }
+  CFRelease(frame_setter);
   return line_ranges;
 }