[ios] Convert GN libs lists to frameworks in //ios/components.

GN recently added support for Apple frameworks to link, rather than
overloading the libs lists. This pulls .frameworks out of the libs
lists, so that GN can stop supporting .frameworks in libs in the
future.

Bug: 1052560
Change-Id: I8060c8baea8424c9ee999a4db99159320268f0b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2277726
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784419}

ios/components/ui_util/BUILD.gn

@@ -4,7 +4,7 @@ source_set("ui_util") {
     "dynamic_type_util.h",
     "dynamic_type_util.mm",
   ]
-  libs = [ "UIKit.framework" ]
+  frameworks = [ "UIKit.framework" ]
   deps = [ "//base" ]
 }