Release map canvas properly

[Joonalai]

This PR:

• Releases map canvas properly after test session
• Updates development dependencies
• Sets QGIS 3.16 as the lowest officially supported version to be able to use the latest development tools

[codecov-commenter]

Codecov Report

Patch coverage: 66.66% and project coverage change: +0.19 :tada:

Comparison is base (f99a323) 54.48% compared to head (9d6a5f2) 54.68%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #29 +/- ## ========================================== + Coverage 54.48% 54.68% +0.19% ========================================== Files 7 7 Lines 468 470 +2 ========================================== + Hits 255 257 +2 Misses 213 213 ``` | Flag | Coverage Δ | | |---|---|---| | pytest | `54.68% <66.66%> (+0.19%)` | :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=GispoCoding#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/29?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding) | Coverage Δ | | |---|---|---| | [src/pytest\_qgis/qgis\_bot.py](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/29?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding#diff-c3JjL3B5dGVzdF9xZ2lzL3FnaXNfYm90LnB5) | `66.66% <ø> (ø)` | | | [src/pytest\_qgis/pytest\_qgis.py](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/29?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding#diff-c3JjL3B5dGVzdF9xZ2lzL3B5dGVzdF9xZ2lzLnB5) | `52.69% <66.66%> (+0.39%)` | :arrow_up: |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[Joonalai]

@LKajan can you review this?