Remove one unnecessary comma in line 763 in reviewboard.Hostingsvcs.github. Line 763 is an assignment statement, which originally ends with a comma. This comma causes some problems:

The variable is coerced into being a tuple istead of a str because of the comma, which is unexpected.
It is confusing and against coding style.

The change avoids future problems caused by this inappropriate typecasting behaviour and keeps coding style consistent.

Passed original unit tests in reviewboard.Hostingsvcs.tests.