docs: also fix prose version reference flagged by CodeRabbit

Line 13 still said 'Verify that 2.2.0 is readable' after the install
command was updated to @2.2.3. Align prose with the pin to remove the
version mismatch within the Quick Start section.

(cherry picked from commit b0b955541f)

docs/ANTIGRAVITY-GUIDE.md

@@ -10,7 +10,7 @@ below.
 
 ## Quick start
 
-Verify that 2.2.0 is readable from the registry, then run the pinned package
+Verify that 2.2.3 is readable from the registry, then run the pinned package
 from the project you want to configure:
 
 ```bash