Remove the flag -Wno-unused-lambda-capture completely

Now this flag is unnecessary.

Bug: 681136
Change-Id: I76d762a7d2d36b42a0556cfd4667731d79cbc01a
Reviewed-on: https://chromium-review.googlesource.com/c/1316949Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605816}

build/config/compiler/BUILD.gn

@@ -1606,13 +1606,6 @@ config("no_chromium_code") {
       # suppressing them individually, we just blanket suppress them here.
       "-Wno-unused-variable",
     ]
-
-    if (!is_nacl) {
-      cflags += [
-        # TODO(hans): https://crbug.com/681136
-        "-Wno-unused-lambda-capture",
-      ]
-    }
   }
 
   configs = [ ":default_warnings" ]