Remove the unused test/plugin.html file

Change-Id: Icb14746d65eca8cd9fe3be0c686de08014813fcd

polygerrit-ui/app/.eslintrc.js

diff --git a/polygerrit-ui/app/.eslintrc.js b/polygerrit-ui/app/.eslintrc.js
index e7506e0..ab9732a 100644
--- a/polygerrit-ui/app/.eslintrc.js
+++ b/polygerrit-ui/app/.eslintrc.js
@@ -219,7 +219,7 @@
       }
     },
     {
-      "files": ["samples/**/*.js", "**/test/plugin.html"],
+      "files": ["samples/**/*.js"],
       "globals": {
         // Settings for samples. You can add globals here if you want to use it
         "Gerrit": "readonly",

polygerrit-ui/app/elements/test/plugin.html

diff --git a/polygerrit-ui/app/elements/test/plugin.html b/polygerrit-ui/app/elements/test/plugin.html
deleted file mode 100644
index ecd9007..0000000
--- a/polygerrit-ui/app/elements/test/plugin.html
+++ /dev/null
@@ -1,44 +0,0 @@
-<dom-module id="my-plugin">
-  <script>
-    Gerrit.install(plugin => {
-      plugin.registerStyleModule('app-theme', 'myplugin-app-theme');
-      plugin.registerStyleModule('app-theme-light', 'myplugin-app-theme-light');
-      plugin.registerStyleModule('app-theme-dark', 'myplugin-app-theme-dark');
-    });
-  </script>
-</dom-module>
-
-<dom-module id="myplugin-app-theme">
-  <template>
-    <style>
-      html {
-        --primary-text-color: #F00BAA;
-      }
-    </style>
-  </template>
-</dom-module>
-
-<dom-module id="myplugin-app-theme-light">
-  <template>
-    <style>
-      html {
-        --header-background-color: #F01BAA;
-        --header-title-content: "MyGerrit";
-        --footer-background-color: #F02BAA;
-      }
-    </style>
-  </template>
-</dom-module>
-
-<dom-module id="myplugin-app-theme-dark">
-  <template>
-    <style>
-      html {
-        --primary-text-color: red;
-        --header-background-color: black;
-        --header-title-content: "MyGerrit Dark";
-        --footer-background-color: yellow;
-      }
-    </style>
-  </template>
-</dom-module>