docs: fix spelling in pivot_longer explanation (#9780)

Fixing typo in `pivot_longer` explanation. 

I have also submitted an upstream PR to catch this in the future,
although it's unlikely we'll re-encounter it.

codespell-project/codespell#3507

ibis/expr/types/relations.py

@@ -3759,7 +3759,7 @@ def pivot_longer(
         │ ABW     │ SP.URB.TOTL │ 2004   │ 42317.0 │
         └─────────┴─────────────┴────────┴─────────┘
 
-        `pivot_longer` has some preprocessing capabiltiies like stripping a prefix and applying
+        `pivot_longer` has some preprocessing capabilities like stripping a prefix and applying
         a function to column names
 
         >>> billboard = ibis.examples.billboard.fetch()