fix: unexpected arg 'label'

[wjunLu]

There is an error in bioconda_utils/cli.py:

Currently, handle_merged_pr calls build with setting arg label, see https://github.com/bioconda/bioconda-utils/blob/41b24166f8e24b2155d4bb2dcfff94c10f46dfb7/bioconda_utils/cli.py#L551C5-L560C10:

if res == UploadResult.NO_ARTIFACTS and fallback == 'build':
        success = build(
            recipe_folder,
            config,
            git_range=git_range,
            anaconda_upload=not dryrun,
            mulled_upload_target=quay_upload_target if not dryrun else None,
            mulled_test=True,
            label=label,
        )

But build is defined as following:

def build(recipe_folder, config, packages="*", git_range=None, testonly=False,
          force=False, docker=None, mulled_test=False, build_script_template=None,
          pkg_dir=None, anaconda_upload=False, mulled_upload_target=None,
          build_image=False, keep_image=False, lint=False, lint_exclude=None,
          check_channels=None, n_workers=1, worker_offset=0, keep_old_work=False,
          mulled_conda_image=pkg_test.MULLED_CONDA_IMAGE,
          docker_base_image=None,
          record_build_failures=False,
          skiplist_leafs=False,
          disable_live_logs=False,
          exclude=None,
          subdag_depth=None):

There is no arg label in build, this will fail when res == UploadResult.NO_ARTIFACTS and fallback == 'build'.

I think maybe it never entered this branch before, so never an error encountered.