don't rely on PR description to identify the package

[ericLemanissier]

an example of failure is conan-io/conan-center-index#9330, which is associated by your bot to tensorflow-lite/2.8.0 because this reference happens to appear in the pull request description, but the PR is in fact for xnnpack/cci.20211210
A more reliable solution would be to do the following:
for each updatable package (package/version)and for each pull request
-download the PR's recipes/package/config.yml file

• search if version is listed in config.yml

if the quadratic nature of this solution seems inapropriate, then you could checkout each PR's branch, and find the package it modifies by calling git show --first-parent --name-only