yamllinter: raise if a version has patches but no sources

[ericLemanissier]

This can happen if "someone" removes an outdated version, but forgets to check if there are patches for this version
(it happened to me yesterday)

---

• I've read the contributing guidelines.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[ericLemanissier]

We just found offenders:

• https://github.com/conan-io/conan-center-index/actions/runs/3765974101/jobs/6401984560#step:9:5494 ->

  conan-center-index/recipes/libcurl/all/conandata.yml

  Line 33 in 8b3c7ac

  "7.79.0":

• https://github.com/conan-io/conan-center-index/actions/runs/3765974101/jobs/6401984560#step:9:6276 ->

  conan-center-index/recipes/libpq/all/conandata.yml

  Line 24 in 8b3c7ac

  "13.3":

• https://github.com/conan-io/conan-center-index/actions/runs/3765974101/jobs/6401984560#step:9:7538 ->

  conan-center-index/recipes/mdnsresponder/all/conandata.yml

  Line 18 in 8b3c7ac

  "878.200.35-opt":

[prince-chrismc]

• https://github.com/conan-io/conan-center-index/actions/runs/3765974101/jobs/6401984560#step:9:7538 -

This one I remember did weird stuff

conan-center-index/recipes/mdnsresponder/all/conanfile.py

Line 136 in 8b3c7ac

for patch in self.conan_data.get("patches", {}).get("{}-opt".format(self.version), []):

[ericLemanissier]

just to be clear: one of the job failed, but it is not a blocker for this PR

[paulharris]

LGTM