[BER-2026] Make it platinum, not platin

Author: range

data/events/2026/berlin/main.yml

@@ -116,8 +116,8 @@ sponsors_accepted : "yes" # Whether you want "Become a XXX Sponsor!" link
 # unlimited sponsors, omit the max attribute or set it to 0. If you want to prevent all
 # sponsorship for a specific level, it is best to remove the level.
 sponsor_levels:
-  - id: platin
-    label: Platin
+  - id: platinum
+    label: Platinum
 #    max: 10
   - id: gold
     label: Gold