fix(ngMock): trigger digest with $httpBackend.verifyNoOutstandingRequest

[katemihalikova]

To be consistent with $httpBackend.verifyNoOutstandingExpectation and $httpBackend.flush
Fixes #13506

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[katemihalikova]

Signed, thx.

[googlebot]

CLAs look good, thanks!

[glebec]

If #14235 is accepted we should add similar documentation to this parameter.

[gkalpak]

I added a test, tweaked the commit message (to add a more detailed description and a breaking change notice) and landed.

Thx @katemihalikova!