ansible: Install libcurl3-gnutls from bookworm-backports

ansible: Install libcurl3-gnutls from bookworm-backports

In the CI builds, we're seeing an issue where certain projects hang
and fail to checkout the gerrit refs.

Eg. ```
git init .
git fetch --tags --force --progress -- \
  https://review.lttng.org/babeltrace \
  +refs/heads/*:refs/remotes/origin/*
git fetch --tags --force --progress -- \
  https://review.lttng.org/babeltrace \
  refs/changes/*:refs/changes/*
```

Not all repositories are affected. There seems to be some type of
content in the gerrit repository that triggers the issue.
After some testing, the version of libcurl3-gnutls available in
bookworm-backports (8.4.0-2~bpo12+1) doesn't seem to be affected
while the version in Debian bookworm (7.88.1-10+deb12u4) fails.

Fetches via SSH are not affected.

Refs #1532

Change-Id: If4b8ca62d5a512c7cccc2225b180b91d3832987d
Signed-off-by: Kienan Stewart <kstewart@efficios.com>