Remove logcat functionality from mozrunner

When testing locally, logcat can be run easily; in CI, mozharness scripts manage
logcat and save the logcat as a test artifact.

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1497566
gecko-commit: 11f33f3c73b4d58511d16cc0fbfcf8fa9363084f
gecko-integration-branch: central
gecko-reviewers: automatedtester
diff --git a/tools/wptrunner/wptrunner/browsers/fennec.py b/tools/wptrunner/wptrunner/browsers/fennec.py
index ddb1667..56c2163 100644
--- a/tools/wptrunner/wptrunner/browsers/fennec.py
+++ b/tools/wptrunner/wptrunner/browsers/fennec.py
@@ -217,16 +217,6 @@
 
         self.runner.start(debug_args=debug_args, interactive=self.debug_info and self.debug_info.interactive)
 
-        # gecko_log comes from logcat when running with device/emulator
-        logcat_args = {
-            "filterspec": "Gecko",
-            "serial": self.runner.device.app_ctx.device_serial
-        }
-        # TODO setting logcat_args["logfile"] yields an almost empty file
-        # even without filterspec
-        logcat_args["stream"] = sys.stdout
-        self.runner.device.start_logcat(**logcat_args)
-
         self.runner.device.device.forward(
             local="tcp:{}".format(self.marionette_port),
             remote="tcp:{}".format(self.marionette_port))