fix: pixi-shell: bump timeout to 3 secs, fix docs link

[wolfv]

Part of #3525

[noamgot]

@wolfv I see you already opened this PR, so just adding my 2 cents for the typos in the pixi shell docs page (https://pixi.sh/latest/advanced/pixi_shell/):

1. remove the redundant single quotes around $manifest_path (in the Emulating conda activate With Pixi section)
2. since you've changed the timeout to 3 seconds, it should be fixed in this page as well (the one second timeout is described, just change it to 3)

thanks!

[wolfv]

Fixed up the docs, thank you!

[Hofer-Julian]

Great!