[ci] fix shellcheck warnings in CI scripts #9106

Job	Run time
r-package (ubuntu-latest, gcc, R 3.6, cmake)	4m 6s
r-package (ubuntu-latest, gcc, R 4.3, cmake)	4m 7s
r-package (clang17, R-devel)	4m 5s
r-package (ubuntu-latest, clang, R 4.3, cmake)	4m 6s
r-package (clang18, R-devel)	4m 7s
r-package (macos-13, gcc, R 4.3, cmake)	4m 17s
r-package (clang19, R-devel)	4m 9s
r-package (macos-13, clang, R 4.3, cmake)	4m 21s
r-package (gcc14, R-devel)	4m 7s
r-package (intel, R-devel)	4m 7s
r-package (windows-latest, MINGW, R 3.6, cmake)	4m 25s
r-package (windows-latest, MINGW, R 4.3, cmake)	4m 8s
r-package (windows-2019, MSVC, R 3.6, cmake)	4m 6s
r-sanitizers (ubuntu-latest, R-devel, gcc ASAN/UBSAN)	4m 4s
r-sanitizers (ubuntu-latest, R-devel, clang ASAN/UBSAN)	4m 8s
r-package (windows-2022, MSVC, R 4.3, cmake)	4m 8s
r-package (windows-latest, MINGW, R 3.6, cran)	4m 6s
r-package (windows-latest, MINGW, R 4.3, cran)	4m 6s
r-package (ubuntu-latest, gcc, R 4.3, cran)	4m 7s
r-package (macos-13, clang, R 4.3, cran)	4m 18s
r-package (macos-14, clang, R 4.3, cran)	4m 18s
all-r-package-jobs-successful	2s
	1h 27m 28s

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