chore: bump tslint and fix failure (#9667)

Bumps to the latest version of tslint and fixes a failure that wasn't being caught before.

Author: crisbeto

package-lock.json

@@ -121,7 +121,7 @@
     "stylelint": "^8.4.0",
     "ts-node": "^3.0.4",
     "tsconfig-paths": "^2.3.0",
-    "tslint": "^5.8.0",
+    "tslint": "^5.9.1",
     "tsutils": "^2.6.0",
     "typescript": "~2.5.3",
     "uglify-js": "^2.8.14",

package.json

@@ -24,7 +24,7 @@ export abstract class DateAdapter<D> {
 
   /** A stream that emits when the locale changes. */
   get localeChanges(): Observable<void> { return this._localeChanges; }
-  protected _localeChanges= new Subject<void>();
+  protected _localeChanges = new Subject<void>();
 
   /**
    * Gets the year component of the given date.