Fix cluster file loading bug in pdb_data.py

[amorehead]

Reference Issues/PRs

Fixes a cluster file loading bug in pdb_data.py,

What does this implement/fix? Explain your changes

The PDBManager's from_fasta() function already prefixes its input filename argument with self.root_dir /, so one needs to remove this prefix in functions that call from_fasta() (to avoid a double prefix that causes a file not found error).

What testing did you do to verify the changes in this PR?

I tested this change locally.

Pull Request Checklist

• Added a note about the modification or contribution to the ./CHANGELOG.md file (if applicable)
• Added appropriate unit test functions in the ./graphein/tests/* directories (if applicable)
• Modify documentation in the corresponding Jupyter Notebook under ./notebooks/ (if applicable)
• Ran python -m py.test tests/ and make sure that all unit tests pass (for small modifications, it might be sufficient to only run the specific test file, e.g., python -m py.test tests/protein/test_graphs.py)
• Checked for style issues by running black . and isort .

[sonarcloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud