fixup typo README

Co-authored-by: Jubilee <[email protected]>

pgrx-examples/decoder/README.md

@@ -7,7 +7,7 @@ using [Logical Decoding] and export them in JSON format using [serde].
 ## Principles
 
 * Postgres triggers various callbacks at the different stages of a transaction
-* The decoder defines some of these callbacks : begin, change, commit, etc.
+* The decoder defines some of these callbacks: begin, change, commit, etc.
 * The callbacks extract the changes made during the transaction
 * They build Rust structs (Action, Tuple) to represent those changes
 * The structs are then serialized into JSON