code_style: remove unused namespace using #3733

Job	Run time
Prepare version string	4s
Build / Build Windows x64	3m 36s
Build / Build Windows ARM64	3m 40s
Build / Build Linux (arm64)	3m 13s
Build / Build macOS (Apple Silicon)	3m 20s
Build / Build Linux	3m 14s
Build / Build macOS (Intel)	3m 7s
Package / Package Windows (win-x64)	32s
Package / Package macOS (osx-x64)	19s
Package / Package Linux (linux-x64)	54s
Package / Package Linux (linux-arm64)	50s
Package / Package Windows (win-arm64)	29s
Package / Package macOS (osx-arm64)	21s
	23m 39s

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