[CI][Dev] Fix shellcheck errors in the ci/scripts/r_install_system_dependencies.sh

### Describe the enhancement requested This is the sub issue #44748. * SC2223: This default assignment may cause DoS due to globbing. Quote it. * SC2006: Use $(...) notation instead of legacy backticked `...`. ``` shellcheck r_install_system_dependencies.sh r_install_system_dependencies.sh: r_install_system_dependencies.sh: openBinaryFile: does not exist (No such file or directory) palolovalley:arrow hsato$ shellcheck ci/scripts/r_install_system_dependencies.sh In ci/scripts/r_install_system_dependencies.sh line 22: : ${ARROW_SOURCE_HOME:=/arrow} ^--------------------------^ SC2223 (info): This default assignment may cause DoS due to globbing. Quote it. In ci/scripts/r_install_system_dependencies.sh line 25: if [ "`which dnf`" ]; then ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`. Did you mean: if [ "$(which dnf)" ]; then In ci/scripts/r_install_system_dependencies.sh line 27: elif [ "`which yum`" ]; then ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`. Did you mean: elif [ "$(which yum)" ]; then In ci/scripts/r_install_system_dependencies.sh line 29: elif [ "`which zypper`" ]; then ^------------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`. Did you mean: elif [ "$(which zypper)" ]; then In ci/scripts/r_install_system_dependencies.sh line 31: elif [ "`which apk`" ]; then ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`. Did you mean: elif [ "$(which apk)" ]; then In ci/scripts/r_install_system_dependencies.sh line 59: if [ "$ARROW_S3" == "ON" ] && [ -f "${ARROW_SOURCE_HOME}/ci/scripts/install_minio.sh" ] && [ "`which wget`" ]; then ^----------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`. Did you mean: if [ "$ARROW_S3" == "ON" ] && [ -f "${ARROW_SOURCE_HOME}/ci/scripts/install_minio.sh" ] && [ "$(which wget)" ]; then For more information: https://www.shellcheck.net/wiki/SC2223 -- This default assignment may cause... https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le... ``` ### Component(s) Continuous Integration