Remove redundant corepack pnpm version specification

[wesleybl]

The corepack use pnpm@9 command is unnecessary since corepack is already enabled and will automatically detect and use the appropriate pnpm version based on the project configuration. This change simplifies the Dockerfile and maintains consistency with other Docker images in the project.

I was going to upgrade to pnpm 10. But I saw that it wasn't necessary, and the only reference to pnpm 9 is there.

Ref: plone/volto#7239

[wesleybl]

@sneridagh @davisagli @ericof can you take a look please?

[sneridagh]

@wesleybl We had to do this because we had problems if it was not set (specially when 10 was released). If 11 is released, we will have the same pitfall.

Another issues is that I don't know if we can do it for 18, without it being breaking. For 19, could be that is ok.
@davisagli @ericof we will have to investigate it.

[wesleybl]

@wesleybl We had to do this because we had problems if it was not set (specially when 10 was released). If 11 is released, we will have the same pitfall.

@sneridagh I don't understand why this line is necessary when pnpm 11 is released. What problem occurred when pnpm 10 was released?

This line serves more to tell the project which pnpm version it should use. But cookieplone already specifies which pnpm version to use in its package.json. So it doesn't make sense to run corepack use pnpm@9 here. Even so, it will install the latest version of 9, which is currently 9.15, but the current version specified in cookieplone is 9.1.1. So, when pnpm start:prod is run here:

plone-frontend/pnpm/Dockerfile.prod

Lines 36 to 40 in 137562b

	# Entrypoint would be pnpm
	ENTRYPOINT [ "pnpm" ]
	# And the image will run in production mode
	CMD ["start:prod"]

corepack would detect that version 9.15 is not the one required by package.json and would download version 9.1.1.

One advantage of already having the correct version installed would be that the container startup would take a few seconds less time to load, since the correct version would already be installed. But it would have to be the same version as cookieplone, not @9. Even so, I don't think it's worth having to keep the version here, just to start the container 2 seconds faster.

Another issues is that I don't know if we can do it for 18, without it being breaking.

I don't think the changes will be breaking. It will work with pnpm 9 as well, if the user wants to continue using 9.

[wesleybl]

@ericof @davisagli Can you take a look here please?