fix(ngRepeat): allow extra whitespaces in (key,value) of ngRepeat

Request Type: 

How to reproduce: 

Component(s): ngRepeat

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**



**Other Comments:**

Whitespaces allowed in (key,value) expression of ngRepeat.

e.g. (  aaa  ,   bbb  ) will be accepted by parser

closes #6827