Fixes #7515
The snap cannot correctly unpack the env declaration, since python is not contained in the snap but is in a base snap (core18)
This fix reverts only the version in the snap, so the other builds still work with the env variables.

The flatpak needs checking.

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.