Fix mass meeting slides link in join.md

Updated the link to the mass meeting slides for accuracy.

Author: doamydebug

config/join.md

@@ -20,7 +20,7 @@ MDST is hosting two mass meetings this year. Join us on January 12, 2026 from 6:
 
 Take a look at our slides and recording from last semester's mass meeting:
 
-<p className="md-button-wrapper"><a className="md-button" href="https://docs.google.com/presentation/d/1t3gDbbn2A0olplKDnWa6BW6DsYrYDCFih-7RqGtmZMo/edit?usp=sharing"> Mass Meeting Slides</a></p>
+<p className="md-button-wrapper"><a className="md-button" href="https://docs.google.com/presentation/d/1ilkQgO_VfX2ejss3pIXln1ets2vgDeXoJFd-Ko37gf4/edit?usp=sharing"> Mass Meeting Slides</a></p>
 
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