[Stylecop] Fix new issues and treat warnings as errors

[ceciliaavila]

Proposed Changes

• Modify the ruleSet file to treat StyleCop's warnings as errors.
• Fix the newly introduce Stylecop issues.

[coveralls]

Pull Request Test Coverage Report for Build 71985

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 77.061%

---

Files with Coverage Reduction	New Missed Lines	%
/libraries/Microsoft.Bot.Builder.AI.QnA/Utils/GenerateAnswerUtils.cs	3	94.83%

Totals
Change from base Build 71783:	0.0%
Covered Lines:	4955
Relevant Lines:	6430

---

💛 - Coveralls

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.3.1

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.3.1
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.3.1