fix: duplicate slice test + message

[lczyk]

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• remove needless \") from duplicate slices message
• add stripBase to have only relative slice path in the message

[github-actions]

Command	Mean [s]	Min [s]	Max [s]	Relative
BASE	13.334 ± 0.066	13.228	13.448	1.00
HEAD	13.335 ± 0.090	13.219	13.538	1.00 ± 0.01

[upils]

Good catch, thanks! Also thanks for adding the missing test.