chore(AIP-111): fix typo (#1561)

Author: maroth96

aip/general/0111.md

@@ -64,7 +64,7 @@ specified in the other AIPs ([AIP-131][] through [AIP-135][]).
 - [Declarative clients][] operate on the management plane exclusively.
 - Data planes are often on the critical path of user-facing functionality, and
   therefore:
-  - Have higher availabilty requirements than management planes.
+  - Have higher availability requirements than management planes.
   - Are more performance-sensitive than management planes.
   - Require higher-throughput than management planes.