replace the link to packages by maintainer email

[avallecam]

The current link is not getting anywhere:

.github/OFFBOARDING.md

Line 10 in 8681a6b

* Link to see packages maintained on CRAN by a given email address: <https://cran.r-project.org/web/checks/check_results_hugo_at_data.org.html>

More stable options could be:

• https://cran.r-project.org/web/checks/check_results_adam.kucharski_at_lshtm.ac.uk.html
• https://cran.r-project.org/web/checks/check_results_hadley_at_posit.co.html