fix: live preview event handler leak causing inconcsitant lp bugs caught by integ tests failures

the EditorManager.off(`activeEditorChange. code was accidentaly deleted during refactoring changes

Author: abose

src/LiveDevelopment/MultiBrowserImpl/documents/LiveDocument.js

@@ -79,7 +79,7 @@ define(function (require, exports, module) {
      * Closes the live document, terminating its connection to the browser.
      */
     LiveDocument.prototype.close = function () {
-
+        EditorManager.off(`activeEditorChange.LiveDocument-${this.doc.file.fullPath}`);
         this._clearErrorDisplay();
         this._detachFromEditor();
     };

test/spec/LiveDevelopmentMultiBrowser-test.js

@@ -924,14 +924,15 @@ define(function (require, exports, module) {
         }, 30000);
 
         it("focus test: should html live previews never take focus from editor", async function () {
-            // this test may fail if the test window doesn't have focus
-            await awaitsForDone(SpecRunnerUtils.openProjectFiles(["inline-style.html"]),
+            await awaitsForDone(SpecRunnerUtils.openProjectFiles(["simple1.html"]),
                 "SpecRunnerUtils.openProjectFiles simple1.html");
 
             await waitsForLiveDevelopmentToOpen();
+            await _editFileAndVerifyLivePreview("simple1.html", { line: 11, ch: 45 }, 'hello world ',
+                "testId", "Brackets is hello world awesome!");
 
             let iFrame = testWindow.document.getElementById("panel-live-preview-frame");
-            expect(iFrame.src.endsWith("inline-style.html")).toBeTrue();
+            expect(iFrame.src.endsWith("simple1.html")).toBeTrue();
             iFrame.focus(); // live preview has focus but it can take html focus, the live preview has to
             // delegate focus to editor explicitly in case of html files.
             expect(testWindow.document.activeElement).toEqual(iFrame);