[Engineering] Lower time for botframework-connector tests

[denscollo]

Address #2338

Description

This pull request updates the tests for the BotFramework-connector library by arranging variables to be reused, removing duplicated tests, and removing unused declarations.

Specific Changes

auth.test.js:

• Moved the variables header and credentials (split in genericCredentials and emptyCredentials) to the top of the tests to be created once and used in multiple tests.
• Removed duplicated test validateIdentity should fail if unauthenticated, that does the same as the test validateIdentity should fail if no identity for the GovernmentChannelValidator and EnterpriseChannelValidator describes.
• Removed unused claims declaration.
• Removed extras ;.

connector.test.js:

• Remove unused declarations.

simpleCredentialProvider.test.js:

• Removed superfluous assert, the removed assert is already tested in the constructor's test.

Testing

After the changes, the code coverage is not reduced.