chore: Bump `proxy-agent` to version 6.3.0

[congminh1254]

Closes: #843

[coveralls]

Pull Request Test Coverage Report for Build 5596755950

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.747%

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Totals
Change from base Build 5586603323:	0.0%
Covered Lines:	2939
Relevant Lines:	3037

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💛 - Coveralls