feature: add frozen string magic comment #8

Job	Run time
Nightly / Puppet7 gem on Ruby 2.7 on Linux	1m 44s
Released / Puppet7 gem on Ruby 2.7 on Linux	1m 6s
Nightly / Puppet8 gem on Ruby 3.1 on Linux	44s
Released / Puppet8 gem on Ruby 3.1 on Linux	35s
Nightly / Puppet7 gem on Ruby 2.7 on macOS	3m 35s
Released / Puppet7 gem on Ruby 2.7 on macOS	3m 14s
Nightly / Puppet8 gem on Ruby 3.1 on macOS	2m 15s
Released / Puppet8 gem on Ruby 3.1 on macOS	1m 23s
Nightly / Puppet7 gem on Ruby 2.7 on Windows	6m 22s
Released / Puppet7 gem on Ruby 2.7 on Windows	4m 40s
Nightly / Puppet8 gem on Ruby 3.1 on Windows	3m 24s
Released / Puppet8 gem on Ruby 3.1 on Windows	3m 53s
	32m 55s

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