fix: [#4204] Fix remaining eslint warnings - remaining issues

[ceciliaavila]

Addresses #4204
#minor

Description

This PR fixes the new ESLint and JSDoc issues introduced before enabling lint check.

Specific Changes

• Applied auto-fixes with yarn lint --fix
  • Fix indentation
• Applied manual fixes for:
  • Missing documentation in the appCredentials class.

Testing

Here we can see the yarn lint command running without issues.

[coveralls]

Pull Request Test Coverage Report for Build 2672032686

• 8 of 8 (100.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.004%) to 84.483%

---

Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-core/src/testAdapter.ts	1	89.68%

Totals
Change from base Build 2665681549:	-0.004%
Covered Lines:	19900
Relevant Lines:	22308

---

💛 - Coveralls

[ceciliaavila]

Hi @tracyboehrer, here is the fix for the new lint issues. After merging this PR, the checks on #4241 should pass.