Partial revert of "Attempt to disable tab_capture_end2end_tests on the trybots"

This partially reverts:
https://codereview.chromium.org/2828143007
to fix broken GPU Linux builder.

BUG=714976,714336
TBR=dpranke@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2842963003
Cr-Commit-Position: refs/heads/master@{#467318}

testing/buildbot/gn_isolate_map.pyl

@@ -896,7 +896,7 @@
   "tab_capture_end2end_tests": {
     # TODO(dpranke), TODO(crbug.com/714336): What is the right label to
     # have here (and/or the right way to run this?).
-    "label": "//chrome/test:tab_capture_end2end_tests",
+    "label": "//chrome/test:browser_tests",
     "type": "gpu_browser_test",
     "gtest_filter": "CastStreamingApiTestWithPixelOutput.EndToEnd*:TabCaptureApiPixelTest.EndToEnd*",
   },