docs: adjust version in maintenance (#1484)

0.20.0 looks weird given that the library is already stable.

Author: krzema12

MAINTENANCE.md

@@ -11,5 +11,5 @@ It currently happens monthly, around the beginning of each month. We don't need
    VERSION=${COMMIT_TITLE#"chore: prepare for releasing version "}
    git tag -a "v$VERSION" -m "chore: release version $VERSION" && git push origin "v$VERSION"
    ```
-1. On `main` branch, change version to prepare for the next development cycle, e.g. if it was `0.20.1-SNAPSHOT` before and we released it as `0.21.0`, change the version to `0.21.1-SNAPSHOT`.
+1. On `main` branch, change version to prepare for the next development cycle, e.g. if it was `1.2.3-SNAPSHOT` before and we released it as `1.2.3`, change the version to `1.2.3-SNAPSHOT`.
 1. Ensure that the release job has succeeded.