Get rid of deprecation warnings in computational_resources.py

[danielhollas]

pytest test/test_computational_resources.py would generate 7 deprecation warnings coming from ipywidgets and traitlets.

Step towards fixing #490

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.03% :tada:

Comparison is base (5038966) 79.42% compared to head (1c41819) 79.46%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #508 +/- ## ========================================== + Coverage 79.42% 79.46% +0.03% ========================================== Files 27 27 Lines 3757 3759 +2 ========================================== + Hits 2984 2987 +3 + Misses 773 772 -1 ``` | [Flag](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab) | Coverage Δ | | |---|---|---| | [python-3.10](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab) | `79.46% <100.00%> (+0.03%)` | :arrow_up: | | [python-3.8](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab) | `79.49% <100.00%> (+0.03%)` | :arrow_up: | | [python-3.9](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab) | `79.49% <100.00%> (+0.03%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files Changed](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab) | Coverage Δ | | |---|---|---| | [aiidalab\_widgets\_base/databases.py](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab#diff-YWlpZGFsYWJfd2lkZ2V0c19iYXNlL2RhdGFiYXNlcy5weQ==) | `94.11% <ø> (+0.65%)` | :arrow_up: | | [aiidalab\_widgets\_base/computational\_resources.py](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab#diff-YWlpZGFsYWJfd2lkZ2V0c19iYXNlL2NvbXB1dGF0aW9uYWxfcmVzb3VyY2VzLnB5) | `70.66% <100.00%> (+0.10%)` | :arrow_up: | | [tests/test\_computational\_resources.py](https://app.codecov.io/gh/aiidalab/aiidalab-widgets-base/pull/508?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidalab#diff-dGVzdHMvdGVzdF9jb21wdXRhdGlvbmFsX3Jlc291cmNlcy5weQ==) | `100.00% <100.00%> (ø)` | |

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