Removing -Wno-write-strings from video_capture_tests.

Bug: webrtc:9251
Change-Id: I6bb182e2ff2676eccdfaca9f608d2134830087f8
Reviewed-on: https://webrtc-review.googlesource.com/80840
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23502}

modules/video_capture/BUILD.gn

@@ -143,12 +143,6 @@ if (!build_with_chromium) {
       sources = [
         "test/video_capture_unittest.cc",
       ]
-
-      cflags = []
-      if (is_linux || is_mac) {
-        cflags += [ "-Wno-write-strings" ]
-      }
-
       ldflags = []
       if (is_linux || is_mac) {
         ldflags += [