cat: Improve performance of formatting. #7008

Job	Run time
Style/format (ubuntu-latest, feat_os_unix)	16s
Style/lint (macos-latest, feat_os_macos)	1m 0s
Style/spelling (ubuntu-latest, feat_os_unix)	1m 0s
Style/Python	6s
Style/lint (windows-latest, feat_os_windows)	1m 59s
Style/toml	11s
Style/lint (ubuntu-latest, feat_os_unix)	42s
	5m 14s

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