[Fix YAML Parsing] Replace deprecated yaml.load() usage and update ruamel.yaml dependencies

[pm25]

What does this PR do?

This PR addresses an issue related to YAML parsing. Specifically, using:

dic = yaml.load(f.read(), Loader=yaml.Loader)

(from semilearn/core/utils/misc.py#L25)

raises the following error with newer versions of ruamel.yaml:

AttributeError: "load()" has been removed, use YAML(typ='rt') instead.

To resolve this, I updated the code to use the recommended interface:

from ruamel.yaml import YAML

yaml = YAML(typ='rt')
with open(yml, 'r', encoding='utf-8') as f:
    dic = yaml.load(f)

I also updated the dependencies in requirements.txt to ensure compatibility:

• ruamel.yaml >= 0.18.0
• ruamel.yaml.clib >= 0.2.7

These versions are required for the YAML(typ='rt') interface to work as expected.

Does your PR introduce any breaking changes? If yes, please list them.

No. I verified that all packages listed in requirements.txt can be installed with their minimal versions without error. I also tested the FixMatch implementation and confirmed that it runs smoothly with the updated YAML handling and dependencies.

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