bump golang to version 1.20

[kobzonega]

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Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: N/A

What is the new behavior?

bump golang version to 1.20 due to the need to use a new version for ydb-go-sdk libraries

# github.com/ydb-platform/ydb-go-sdk/v3/internal/xstring
Error: ../../../go/pkg/mod/github.com/ydb-platform/ydb-go-sdk/v3@v3.74.2/internal/xstring/convert.go:15:16: undefined: unsafe.String
Error: ../../../go/pkg/mod/github.com/ydb-platform/ydb-go-sdk/v3@v3.74.2/internal/xstring/convert.go:23:29: undefined: unsafe.StringData
note: module requires Go 1.20

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