[2.x] Fix delete button visibility in search filters

[hogan-tech]

Description

This PR fixes a UI bug in the Variable List page where the "Delete" (remove filter) button for search filters was not fully visible. The issue was caused by legacy table cell (td) settings in the template, which became problematic after upgrading the Flask-AppBuilder package. The button was partially hidden, with only its right border visible, making it difficult for users to remove filters.

What was changed:

• Adjusted the table cell settings in variable_list.html to ensure the remove filter button is always fully visible and accessible in the Variable List filter UI.

Related Issues

closes: #50296

Related PRs

• Airflow: Add 'Show record' option for variables
• Flask-AppBuilder: fix: filter list UI spacing between elements
• [2.x] Fix pools list page's delete button visibility in search filters

How to reproduce

1. Go to Admin → Variables in the Airflow UI.
2. Click "Add Filter" and select a filter.
3. Observe that the delete (remove filter) button is not fully visible (only the right border shows).

What you think should happen instead

The delete search filter button should be fully visible and easily clickable.

Additional context

• This issue appeared after upgrading Flask-AppBuilder, which changed some default table rendering behaviors.
• The fix is backward-compatible and only affects the Variable List page.

Screenshots

Before:

After:

---

Please review and let me know if further adjustments are needed.

---

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contributors' Guide (https://github.com/apache/airflow/blob/main/contributing-docs/README.rst)
Here are some useful points:

• Pay attention to the quality of your code (ruff, mypy and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
• Consider using Breeze environment for testing locally, it's a heavy docker but it ships with a working Airflow and a lot of integrations.
• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
• Please follow ASF Code of Conduct for all communication including (but not limited to) comments on Pull Requests, Mailing list and Slack.
• Be sure to read the Airflow Coding style.
• Always keep your Pull Requests rebased, otherwise your build might fail due to changes not related to your commits.
  Apache Airflow is a community-driven project and together we are making it better 🚀.
  In case of doubts contact the developers at:
  Mailing List: [email protected]
  Slack: https://s.apache.org/airflow-slack

[pierrejeambrun]

Can you also fix it for the Pools template, that's exactly the same issue. pool_list.html

[hogan-tech]

Can you also fix it for the Pools template, that's exactly the same issue. pool_list.html

Thank you for reviewing. I've created a new PR to fix the same issue in the Pools list page:

[2.x] Fix pools list page's delete button visibility in search filters (#51161)

Please let me know if any further changes are needed.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.