Fix Nuxeo CSV and Template Rendering not compatible with LTS 2021

Steps to reproduce:
Using LTS 2021
Launch nuxeoctl mp-install nuxeo-csv-importer nuxeo-template-rendering

=> addon fails to install: no installation candidate
Expected: addons should be installable on a LTS 2021

Looking at the package.xml file for these addons, we can see that they are wrongly generated (example with https://connect.nuxeo.com/nuxeo/site/marketplace/package/nuxeo-csv?version=2021.15.12 below):

  <platforms>
    <platform>lts-2021.15.12</platform>
  </platforms>

Workaround is to fix manually the package.xml file and add a valid version. Valid sample below:

  <target-platform>
    <name>lts</name>
    <version>[2021.2,)</version>
  </target-platform>

This problem may also happen in other packages, these are only two examples where the issue happened recently and no further check was done.