Cleanup BUILD.gn files from imports like foo:foo

Repalce all occurrences of foo:foo in deps with just foo in BUILD.gn
files.

Done with Sublime regex replace.
Find: \b([-a-zA-Z0-9_]+):+\1\b
In: *.gn
Replace with: \1

Bug: None
Change-Id: I40aba1b14face687a595b852ffe443cb20197611
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/127899
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27225}

rtc_tools/network_tester/BUILD.gn

@@ -45,13 +45,13 @@ if (rtc_enable_protobuf) {
       ":network_tester_packet_proto",
       "../../api/task_queue",
       "../../p2p",
+      "../../rtc_base",
       "../../rtc_base:checks",
       "../../rtc_base:protobuf_utils",
-      "../../rtc_base:rtc_base",
       "../../rtc_base:rtc_base_approved",
       "../../rtc_base:rtc_task_queue",
       "../../rtc_base:sequenced_task_checker",
-      "../../rtc_base/third_party/sigslot:sigslot",
+      "../../rtc_base/third_party/sigslot",
       "//third_party/abseil-cpp/absl/memory",
       "//third_party/abseil-cpp/absl/types:optional",
     ]