test(test/reporters/base.spec.js): Fix Base reporter test failure due to timeout
test(test/reporters/base.spec.js): Fix Base reporter test failure due to timeout

The `Base` reporter's specification verifies reporter can interpret Chai custom error messages. This
test takes ~480ms (lightly loaded CPU), which is _way_ too close to the 500ms timeout. Change
doubles this timeout.

#3524

igwejk/mocha,outsideris/mocha,boneskull/mocha,adamgruber/mocha,igwejk/mocha,mochajs/mocha,outsideris/mocha,adamgruber/mocha,boneskull/mocha,boneskull/mocha,mochajs/mocha,adamgruber/mocha,mochajs/mocha