Fix docs for plugin install via proxy on Windows
Fix docs for plugin install via proxy on Windows

This commit addresses an issue with the docs for plugin install via a
proxy on Windows where the HTTP proxy options were incorrectly
specified.

Relates #23757

strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc