[Refactor] Add pyupgrade pre-commit hook (#2078)

.dev/check_urls.py

.dev/gather_models.py

.dev/generate_benchmark_train_script.py

.dev/log_collector/log_collector.py

.dev/md2yml.py

.pre-commit-config.yaml

docs/en/conf.py

docs/en/stat.py

docs/zh_cn/conf.py

docs/zh_cn/stat.py

mmseg/engine/optimizers/layer_decay_optimizer_constructor.py

mmseg/evaluation/metrics/iou_metric.py

mmseg/models/backbones/beit.py

mmseg/models/backbones/bisenetv1.py

mmseg/models/backbones/bisenetv2.py

mmseg/models/backbones/cgnet.py

mmseg/models/backbones/erfnet.py

mmseg/models/backbones/fast_scnn.py

mmseg/models/backbones/hrnet.py

mmseg/models/backbones/icnet.py