Update esmvaltool run command everywhere in documentation

[bouweandela]

The command to run esmvaltool was changed some time ago, but there were still some old ways of using it in the documentation. This pull request fixes that and a few spelling mistakes.

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Tasks

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[jvegreg]

I have found another reference in esmvaltool/diag_scripts/thermodyn_diagtool/thermodyn_diagnostics.py

For some reason, @ValerioLembo put there a small tutorial. I think this is no longer needed, at least in its actual form

[bouweandela]

Thanks for reviewing @jvegasbsc! I have updated the tutorial by @ValerioLembo so it uses the most recent run command. Could you please have another look?

Indeed I think that extra tutorial in a diagnostic is probably not needed, but I'll leave changing that to @ValerioLembo in a different pull request if he feels the need to change it.

[jvegreg]

The documentation test is failing, but that's because a file you did not touch. I Think this is OK to merge, no?

[bouweandela]

I created an issue for the failing documentation build: Chilipp/autodocsumm#32. For now I'll just change the imports from from itertools import product to import itertools in the affected files, that seems to solve the problem.