Reformat GN files.

`gn format` recently [1] 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.

CL generated with:
$ git ls-files | grep BUILD.gn | xargs gn format
$ gn format build_overrides/build.gni
$ gn format build_overrides/gtest.gni
$ gn format modules/audio_coding/audio_coding.gni
$ gn format webrtc.gni
$ gn format .gn

Plus a few manual changes to add exceptions for
"public_deps" (after changing these lines the presubmit
started to complain).

[1] - https://gn-review.googlesource.com/c/gn/+/6860

Bug: webrtc:11302
Change-Id: Iac29d23c1618ebef925c972e2891cd9f4e8cd613
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/166882
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30334}

common_audio/BUILD.gn

@@ -205,9 +205,7 @@ rtc_library("common_audio_cc") {
 }
 
 rtc_source_set("sinc_resampler") {
-  sources = [
-    "resampler/sinc_resampler.h",
-  ]
+  sources = [ "resampler/sinc_resampler.h" ]
   deps = [
     "../rtc_base:gtest_prod",
     "../rtc_base:rtc_base_approved",
@@ -219,9 +217,7 @@ rtc_source_set("sinc_resampler") {
 
 rtc_source_set("fir_filter") {
   visibility += webrtc_default_visibility
-  sources = [
-    "fir_filter.h",
-  ]
+  sources = [ "fir_filter.h" ]
 }
 
 rtc_library("fir_filter_factory") {

common_audio/third_party/spl_sqrt_floor/BUILD.gn

@@ -10,9 +10,7 @@ import("../../../webrtc.gni")
 
 rtc_library("spl_sqrt_floor") {
   visibility = [ "../..:common_audio_c" ]
-  sources = [
-    "spl_sqrt_floor.h",
-  ]
+  sources = [ "spl_sqrt_floor.h" ]
   deps = []
   if (current_cpu == "arm") {
     sources += [ "spl_sqrt_floor_arm.S" ]