Stop using deprecated mock method macros

[dubious90]

When running fix_format, it will give a complaint like the following:

ERROR: From ./../nbperry-nighthawk/test/test_common/mock_stream.h
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:15: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:18: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:21: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:31: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:34: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:35: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:38: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:41: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead
ERROR: ./../nbperry-nighthawk/test/test_common/mock_stream.h:42: The MOCK_METHODn() macros should not be used, use MOCK_METHOD() instead

I considered this outside the scope of fixing formatting, but as a followup we should probably move to MOCK_METHOD.