uutests: preserve PATH in UCommand to fix NixOS test failures #9523

Job	Run time
L10n/Fluent Syntax Check	16s
L10n/Clap Error Localization Test	55s
L10n/Multi-call Binary Install Test (macos-latest, feat_os_macos)	4m 29s
L10n/Build and Test (ubuntu-latest, feat_os_unix)	2m 21s
L10n/Installation Test (Make & Cargo) (ubuntu-latest, feat_os_unix)	4m 31s
L10n/Multi-call Binary Install Test (ubuntu-latest, feat_os_unix)	2m 57s
L10n/French Integration Test	56s
L10n/Build and Test (macos-latest, feat_os_macos)	3m 3s
L10n/Build and Test (windows-latest, feat_os_windows)	5m 17s
L10n/Locale Support Verification	5m 55s
L10n/Embedded Locale Regression Test	58s
L10n/Locale Embedding - Multicall Binary	2m 1s
L10n/Locale Embedding - Cat Utility	41s
L10n/Locale Embedding - Cargo Install	44s
L10n/Installation Test (Make & Cargo) (macos-latest, feat_os_macos)	4m 42s
L10n/Locale Embedding - Ls Utility	43s
L10n/Locale Embedding Regression Test	3s
	40m 32s

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