[16/20] SPECfile cleanup - explicit definition of Python shebang is not needed
    
    The value we use is the upstream deafult:
    
    | # grep -r -i -e "python_shebang" mariadb-10.5.23-downstream_modified
    | mariadb-10.5.23-downstream_modified/storage/rocksdb/myrocks_hotbackup.py:#!@PYTHON_SHEBANG@
    | mariadb-10.5.23-downstream_modified/cmake/cpack_deb.cmake:SET(PYTHON_SHEBANG "/usr/bin/python3" CACHE STRING "python shebang")
    | mariadb-10.5.23-downstream_modified/cmake/cpack_rpm.cmake:SET(PYTHON_SHEBANG "/usr/bin/python3" CACHE STRING "python shebang")
    | mariadb-10.5.23-downstream_modified/CMakeLists.txt:SET(PYTHON_SHEBANG "/usr/bin/env python3" CACHE STRING "python shebang")
    | mariadb-10.5.23-downstream_modified/CMakeLists.txt:MARK_AS_ADVANCED(PYTHON_SHEBANG)