Fix some minor issues found by sonarqube

[maxnoe]

• Use https where possible
• Use NamedTemporaryFile instead of mktemp

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (c05b493) 92.47% compared to head (30fd288) 92.47%. Report is 2 commits behind head on main.

Files	Patch %	Lines
ctapipe/visualization/bokeh.py	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2466 +/- ## ========================================== - Coverage 92.47% 92.47% -0.01% ========================================== Files 234 234 Lines 19816 19817 +1 ========================================== Hits 18325 18325 - Misses 1491 1492 +1 ```

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