Prevent simultaneous execution of both diagnostics

If both are run at the same time, they may interfere with each other
(as detailed in #51): the failure of one may block the other.

Instead, users have to explicitly start one or the other.
If they want to run both, they can just launch them sequentially.

assets/diagnostics.html

@@ -41,7 +41,6 @@ <h1>Diagnostics</h1>
                 <p>Start a diagnostics test by clicking the appropriate button for your device.</p>
                 <p>Reminder: you'll need to be logged in to your Amazon/Google account.</p>
                 <p>
-                    <button id="test" class="btn btn-primary">Run all diagnostics</button>
                     <button id="google" class="btn btn-primary">Run Google diagnostics</button>
                     <button id="amazon" class="btn btn-primary">Run Amazon diagnostics</button>
                 </p>

src/chrome/pages/diagnostics.ts

@@ -15,7 +15,6 @@ import { Interaction } from '../../common/types';
 import { initErrorHandling } from '../common/errors';
 
 enum Tests {
-    all = 'all',
     google = 'google',
     amazon = 'amazon'
 }
@@ -258,9 +257,6 @@ function runTests(testSuite: Tests) {
 }
 
 function setupDiagnostics() {
-    document.getElementById('test')!.onclick = () => {
-        runTests(Tests.all);
-    };
     document.getElementById('google')!.onclick = () => {
         runTests(Tests.google);
     };