refactor($interpolate): remove unnecessary else

Closes: angular#15575

Author: Nikhil22

src/ng/interpolate.js

@@ -73,9 +73,8 @@ function $InterpolateProvider() {
     if (value) {
       startSymbol = value;
       return this;
-    } else {
-      return startSymbol;
     }
+    return startSymbol;
   };
 
   /**
@@ -91,9 +90,8 @@ function $InterpolateProvider() {
     if (value) {
       endSymbol = value;
       return this;
-    } else {
-      return endSymbol;
     }
+    return endSymbol;
   };