docs: use titles for code blocks

[lars-reimann]

Summary of Changes

Use titles for code blocks to differentiate whether they denote Python code or Safe-DS code. Remove the old comments inside the code blocks that expressed the same thing.

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ MARKDOWN	markdown-link-check	5		0	1.03s
✅ REPOSITORY	git_diff	yes		no	0.11s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

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[codecov]

Codecov Report

Merging #697 (2e1e99b) into main (a15951d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main      #697   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           71        71           
  Lines         9475      9475           
  Branches      1907      1907           
=========================================
  Hits          9475      9475