Make bump_version.sh work with old version of bash

Guillaume Coré

2019-05-21 534b26612c0349243fa898ef5ca5d7805a14d2b2

Make bump_version.sh work with old version of bash

Fix:
./bump_version.sh: line 27: ${response,,}: bad substitution

 tools/bump_version.sh

@@ -27,7 +27,7 @@
        response=${response,,}

        case "${response}" in
            yes|y) true ;;
            yes|y|Y|Yes|YES) true ;;
            *) false ;;
        esac
    fi