Reformat all gn files in /components/prefs.

`gn format` recently changed its formatting behavior
for deps, source, and a few other elements when they
are assigned (with =) single-element lists to be consistent
with the formatting of updates (with +=) with single-element.

Now that we've rolled in a GN binary with the change,
reformat all files so that people don't get presubmit
warnings due to this.

This CL was uploaded by git cl split.

R=battre@chromium.org

Bug: 1041419
Change-Id: Ie1681cb457450139c09ee8651c002ef475744c08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1998318
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731577}

components/prefs/BUILD.gn

@@ -71,9 +71,7 @@ static_library("test_support") {
     "testing_pref_store.h",
   ]
 
-  public_deps = [
-    ":prefs",
-  ]
+  public_deps = [ ":prefs" ]
   deps = [
     "//base",
     "//base/test:test_support",