Adagio: Enable site capability

[osazos]

This PR follows up on #4403 and publicly enables web inventory support (which was available but disabled by default).

Please note that we are currently updating our bidder adapter documentation on prebid.github.io, and the change regarding the placement parameter might temporarily be out of sync until the new documentation is published.

Related doc PR: https://github.com/prebid/prebid.github.io/pull/6327

[bsardo]

@osazos please provide a link to an opened docs PR in the description.

[osazos]

@bsardo the doc PR will be opened on Monday, I'll ping you when it is done. Thanks.

[osazos]

@bsardo the PR description has been updated with the link to the docs PR

[github-actions[bot]]

Code coverage summary

Note:

• Prebid team doesn't anticipate tests covering code paths that might result in marshal and unmarshal errors
• Coverage summary encompasses all commits leading up to the latest one, e929e5dd7576ffa782ba1db6e6173a4e4005dc33

adagio

Refer here for heat map coverage report

github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:20:	Builder		100.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:27:	MakeRequests	80.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:51:	MakeBids	93.8%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:114:	getBidType	100.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:129:	getBidExt	100.0%
total:									(statements)	92.6%