Improve shell code formatting in docs, second part

[enriqueartal]

This is a continuation of #40609 in order to get a bettert format of code blocks, specially concerning copy buttons.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

• Improve shell code formatting in docs #40609: starting point of this PR

[github-actions]

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[enriqueartal]

There are some *.txt files which are not in the tree, they must be generated by some script that I am not able to find. There are some indentation problems in these files avoiding a good copy-and-test behavior.
Any hints?

[enriqueartal]

It seems it is the file src/doc/bootstrap; is there a way to avoid at least the first characters befor $?

[tobiasdiez]

It seems it is the file src/doc/bootstrap; is there a way to avoid at least the first characters befor $?

Maybe it's this one here:

sage/build/bin/sage-print-system-package-command

Lines 36 to 37 in 537c32e

	PROMPT=' $ '
	CONTINUATION=' '

[enriqueartal]

It seems it is the file src/doc/bootstrap; is there a way to avoid at least the first characters befor $?

Maybe it's this one here:

sage/build/bin/sage-print-system-package-command

Lines 36 to 37 in 537c32e

	PROMPT=' $ '
	CONTINUATION=' '

It seems so. Up to some details, the PR is probably ready for review. I am not sure if all the indentations introduced are right and if the changes in sage-print-system-package-command may break elsewhere. I took out the contents in downstream.rst, there is a complain even in the stable branch.