Bug 1800775 follow-up - Fix broken tests. rs=me DONTBUILD

--HG--
extra : rebase_source : 8d5969cc99034a931b03330734eac978447c5df6
extra : absorb_source : 9c54accd51fd11b0ecb5877277385e565eda0ccf

mail/base/test/browser/browser_3paneTelemetry.js

@@ -23,6 +23,10 @@ add_setup(async function() {
   }
   rootFolder.createSubfolder("just a folder", null);
   folders.Other = rootFolder.getChildNamed("just a folder");
+
+  registerCleanupFunction(function() {
+    MailServices.accounts.removeAccount(account, true);
+  });
 });
 
 add_task(async function testFolderOpen() {

mail/test/browser/folder-tree-modes/browser_modeSwitching.js

@@ -72,6 +72,9 @@ add_setup(async function() {
   // Show the Folder Pane header toolbar.
   mc.e("folderPaneHeader").removeAttribute("collapsed");
 
+  Services.xulStore.removeDocument(
+    "chrome://messenger/content/messenger.xhtml"
+  );
   Services.telemetry.clearScalars();
 });