fix(deps): update dependency mysql2 to v3.9.1

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
mysql2 (source)	3.6.5 -> 3.9.1

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Release Notes

sidorares/node-mysql2 (mysql2)

v3.9.1

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Bug Fixes

• types: support encoding for string type cast (#​2407) (1dc2011)

v3.9.0

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Features

• introduce typeCast for execute method (#​2398) (baaa92a)

v3.8.0

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Features

• perf: cache iconv decoder (#​2391) (b95b3db)

Bug Fixes

• stream: premature close when using for await (#​2389) (af47148)
• The removeIdleTimeoutConnectionsTimer did not clean up when the … (#​2384) (18a44f6)
• types: add missing types to TypeCast (#​2390) (78ce495)

v3.7.1

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Bug Fixes

• add condition which allows code in callback to be reachable (#​2376) (8d5b903)

v3.7.0

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Features

• docs: release documentation website (#​2339) (c0d77c0)

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[coveralls]

Pull Request Test Coverage Report for Build 1116e157-0f6c-4a88-83e7-fa22d0f426f8

• 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 92.197%

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Totals
Change from base Build 889ffab4-7a4b-4e81-8f8a-630e303f4274:	0.0%
Covered Lines:	6723
Relevant Lines:	7292

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💛 - Coveralls