[Fix] Change mmcv.dump to mmengine.dump

[ProtossDragoon]

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

Motivation

bash

python3 -m mmocr.ocr \
--det DB_r18 \
--recog CRNN \
demo/demo_text_ocr.jpg \
--pred-out-file temp/demo_text_ocr.pkl

output

Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/root/dev/oss/src_mmocr/mmocr/ocr.py", line 487, in <module>
    main()
  File "/root/dev/oss/src_mmocr/mmocr/ocr.py", line 483, in main
    ocr.readtext(**vars(args))
  File "/root/dev/oss/src_mmocr/mmocr/ocr.py", line 217, in readtext
    return self.inferencer(
  File "/root/dev/oss/src_mmocr/mmocr/apis/inferencers/base_mmocr_inferencer.py", line 149, in __call__
    results = self.postprocess(
  File "/root/dev/oss/src_mmocr/mmocr/apis/inferencers/mmocr_inferencer.py", line 214, in postprocess
    mmcv.dump(results, pred_out_file)
AttributeError: module 'mmcv' has no attribute 'dump'

Modification

dump method was removed from MMCV 2.x. Use mmengine.dump instead.

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with some of those projects.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.

[gaotongxiao]

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[OpenMMLab-Assistant005]

Dear ProtossDragoon,
First of all, we want to express our gratitude for your significant PR in the MMOCR project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
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Thank you again for your contribution❤
Best regards！ @ProtossDragoon