doc: contribute: fix dead link in RFC proposal template

Fix a broken link in the 'contribute/proposals_and_rfcs.rst' file that
pointed to a non-existent Markdown RFC template.

The link previously pointed to:
  .github/ISSUE_TEMPLATE/003_rfc-proposal.md

It has been corrected to point to the actual YAML file:
  .github/ISSUE_TEMPLATE/003_rfc-proposal.yml

Fixes: #92342

Signed-off-by: Gaetan Perrot <gaetan.perrot@spacecubics.com>

Author: moonlight83340

doc/contribute/proposals_and_rfcs.rst

@@ -65,5 +65,5 @@ either disagreement or not enough voiced opinions in order to proceed. Make sure
 to either label it appropriately or include it in the corresponding GitHub
 project in order for it to be examined during the next meeting.
 
-.. _`RFC template`: https://github.com/zephyrproject-rtos/zephyr/blob/main/.github/ISSUE_TEMPLATE/003_rfc-proposal.md
+.. _`RFC template`: https://github.com/zephyrproject-rtos/zephyr/issues/new?template=003_rfc-proposal.yml
 .. _`Zephyr meetings`: https://github.com/zephyrproject-rtos/zephyr/wiki/Zephyr-Committee-and-Working-Groups