[tint][fuzz] Remove tint::wgsl::IRRoundtrip fuzzing pass #5614

Job	Run time
Go Build and Test	26s
CMake-windows-latest-Debug-msvc	14m 41s
CMake-windows-latest-Release-msvc	16m 40s
CMake-ubuntu-latest-Debug-gcc	57m 1s
CMake-ubuntu-latest-Release-gcc	1h 2m 46s
CMake-macos-latest-Debug-clang	19m 0s
CMake-macos-latest-Release-clang	23m 46s
CMake-macos-13-Debug-clang	46m 44s
CMake-macos-13-Release-clang	53m 5s
	4h 54m 9s

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