doc: contribute: fix spelling of advisable in guidelines rst

fix minor typo

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
Co-authored-by: Serge Croisé <SergeCroise@users.noreply.github.com>
diff --git a/doc/contribute/guidelines.rst b/doc/contribute/guidelines.rst
index 48e50de..13b8ce4 100644
--- a/doc/contribute/guidelines.rst
+++ b/doc/contribute/guidelines.rst
@@ -354,7 +354,7 @@
 When opening a new Pull Request, adhere to the following guidelines to ensure
 compliance with Zephyr standards and facilitate the review process.
 
-If in doubt, it's advisible to explore existing Pull Requests within the Zephyr
+If in doubt, it's advisable to explore existing Pull Requests within the Zephyr
 repository. Use the search filters and labels to locate PRs related to changes
 similar to the ones you are proposing.