Fix doc link in selector.py

[quazi-irfan]

resolves #7533

Description

Update the URL link from https://docs.getdbt.com/docs/package-management to https://docs.getdbt.com/reference/node-selection/yaml-selectors for MALFORMED_SELECTOR_ERROR variable at dbt-core/core/dbt/config
/selectors.py as instructed on the issue by dbeatty10.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Irfan Quazi.
This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email [email protected]
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails

[emmyoop]

@cla-bot check

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Irfan Quazi.
This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email [email protected]
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[quazi-irfan]

Fixed email mismatch issue with a new pull request #7755