Bug 30772: Terminology: Replace instances of "reserve" with "hold"

Bug 30772: Terminology: Replace instances of "reserve" with "hold"

There were several templates where we were still using the term
"reserve" instead of "hold." This patch corrects the ones I found,
including in a couple of HTML comments.

To test, apply the patch and confirm that the changes look correct and
affect only the relevant term.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>