minor #10450 typo fix in speaker mentoring (lsmith77)

This PR was submitted for the master branch but it was merged into the 2.8 branch instead (closes #10450).

Discussion
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typo fix in speaker mentoring

should get the link hopefully rendered properly https://symfony.com/doc/current/contributing/community/speaker-mentoring.html

Commits
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66d5519 typo fix in speaker mentoring

Author: javiereguiluz

contributing/community/speaker-mentoring.rst

@@ -33,7 +33,7 @@ public speaker. They can even do practice runs via video chat!
 Furthermore, they can also be an ally when it comes to the day of
 giving the talk at a conference!
 
-A great resource with advice on everything related to`public speaking`_
+A great resource with advice on everything related to `public speaking`_
 is a collection of links maintained by VM (Vicky) Brasseur. It covers
 everything from finding a conference call for proposals, how to
 refine a proposal, to how to put together slide decks to practical