scripts: serie_update.py: support master and main branches

    def clone_cube_repo(self):

        """Clone or fetch a stm32 serie repo"""

        # check whether master branch exist, otherwise use main branch

        master_branch_exist = subprocess.check_output(

            "git ls-remote --heads origin master", cwd=self.stm32cube_serie_path

        ).decode("utf-8")

        if master_branch_exist:

            branch = "master"

        else:

            branch = "main"

        logging.info("Branch used:" + branch)

        if self.stm32cube_serie_path.exists():

            logging.info("fetching repo " + str(self.stm32cube_serie_path))

            # if already exists, then just clean and fetch

            os_cmd(("git", "clean", "-fdx"), cwd=self.stm32cube_serie_path)

            os_cmd(("git", "fetch"), cwd=self.stm32cube_serie_path)

            os_cmd(

                ("git", "reset", "--hard", "master"),

                ("git", "reset", "--hard", branch),

                cwd=self.stm32cube_serie_path,

            )

        else:

        # get the latest version of cube,

        # with the most recent one created being the last entry.

        os_cmd(("git", "checkout", "master"), cwd=self.stm32cube_serie_path)

        os_cmd(("git", "checkout", branch), cwd=self.stm32cube_serie_path)

        self.version_tag = subprocess.check_output(

            "git tag -l", cwd=self.stm32cube_serie_path

        ).splitlines()