Remove unnecessary lines in Ubuntu Clang runner #1693

Job	Run time
GCC build regression check (no tests)	1m 8s
macOS-M1, Clang (x3)	8m 8s
Alpine Linux, musl, 32-bit (assert, x1.5)	17s
MinGW GCC (x0.5)	11m 13s
MSVC (x1)	24m 38s
Nemo.jl	19m 3s
Ubuntu ARM (x5)	12m 22s
Ubuntu Clang, BLAS and examples (x5)	12m 37s
Ubuntu GCC, Code Coverage (x10)	29m 15s
Ubuntu GCC with NTL (assert, x2)	8m 42s
	2h 7m 23s

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