Use removesuffix/removeprefix instead of strip for URL and alias parsing

[eeshsaxena]

Command.create_pull_request derives the owner and repo from the export repository URL like this:

path_parts = url_parts.strip("/").rstrip(".git").split("/")

rstrip takes a set of characters rather than a suffix, so after removing .git it keeps removing any trailing ., g, i or t. Repo names that end in one of those lose characters:

https://github.com/aboutcode-org/vulnerablecode-data.git    -> ['aboutcode-org', 'vulnerablecode-data']
https://github.com/aboutcode-org/vulnerablecode-import.git  -> ['aboutcode-org', 'vulnerablecode-impor']
https://github.com/nexB/scancode-toolkit.git                -> ['nexB', 'scancode-toolk']
https://github.com/aboutcode-org/purldb-git.git             -> ['aboutcode-org', 'purldb-']

The mangled name goes straight into https://api.github.com/repos/{repo_owner}/{repo_name}/pulls, so the export PR fails with a 404 that reads like a permissions problem. It works today only because the repo currently used ends in a.

AdvisoryAlias.url and AliasV2.url have the same idiom:

if alias.startswith("NPM-"):
    id = alias.lstrip("NPM-")

lstrip("NPM-") removes any leading N, P, M or -, so it happens to work for the numeric ids that nodejs/security-wg uses, but it would eat the front of anything else. Since the startswith check has already confirmed the prefix, removeprefix says what is meant and cannot over-strip.

Verification: this repo's suite needs Postgres, which I do not have set up here, so I ran the old and new expressions side by side over the URLs above rather than running pytest. The change is pure string handling on three lines and does not touch any query or model behaviour.