Stop running webview_licenses on the bots

See https://groups.google.com/a/chromium.org/d/msg/chromium-dev/pwyjF_jAf6I/5MeKCBG8BQAJ
for context. Also https://codereview.chromium.org/2312323002 for checklicenses.

BUG=none

Review-Url: https://codereview.chromium.org/2319093002
Cr-Commit-Position: refs/heads/master@{#417232}

testing/buildbot/chromium.linux.json

@@ -1293,12 +1293,6 @@
       {
         "test": "webapk_shell_apk_junit_tests"
       }
-    ],
-    "scripts": [
-      {
-        "name": "webview_licenses",
-        "script": "webview_licenses.py"
-      }
     ]
   },
   "Android Tests (dbg)": {
@@ -1457,12 +1451,6 @@
       {
         "test": "webapk_client_junit_tests"
       }
-    ],
-    "scripts": [
-      {
-        "name": "webview_licenses",
-        "script": "webview_licenses.py"
-      }
     ]
   },
   "Blimp Linux (dbg)": {