chore: remove unnecessary public access modifier

[stevengum]

Part 1 of #3518
#minor

Description:

Removed public access modifier from following packages:

• botbuilder-ai-orchestrator
• botbuilder-ai
• botbuilder-applicationinsights
• botbuilder-azure-queues
• botbuilder-azure

[mdrichardson]

Should we add:

accessibility: 'no-public'

to the .eslintrc? https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/explicit-member-accessibility.md

[stevengum]

@mdrichardson thanks for providing the rule and link. Adding the rule is one of the completion criteria for the issue, and I'll add it to this PR and other PRs on a package basis and make a note to myself to add it to the root config and cleanup the duplicates once all the packages are cleaned up.

[coveralls]

Pull Request Test Coverage Report for Build 916696710

• 55 of 55 (100.0%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.341%

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Totals
Change from base Build 903466753:	0.0%
Covered Lines:	19237
Relevant Lines:	21437

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💛 - Coveralls