Use the root-qualified :wrapper task (#1064)

Replaces the unqualified `wrapper` task name with the
root-project-qualified
`:wrapper` in the two places this repo names it:

- `.github/workflows/demo-job-summary.yml` — the kotlin-dsl sample
invocation
- `docs/wrapper-validation.md` — the guidance for regenerating an
unverifiable
  `gradle-wrapper.jar`

An unqualified `wrapper` matches the task in every project of a
multi-project
build. The root-qualified form is unambiguous, matches the gradle/gradle
convention, and is required under Configure on Demand.

Part of the org-wide rollout tracked in gradle/gradle-private#5228;
original
issue gradle/gradle#37761.

Signed-off-by: Christoph Obexer <cobexer@gradle.com>

Author: cobexer

.github/workflows/demo-job-summary.yml

@@ -46,7 +46,7 @@ jobs:
       run: | 
          ./gradlew tasks --no-daemon
          ./gradlew help check
-         ./gradlew wrapper --gradle-version 8.7 --gradle-distribution-sha256-sum 544c35d6bd849ae8a5ed0bcea39ba677dc40f49df7d1835561582da2009b961d
+         ./gradlew :wrapper --gradle-version 8.7 --gradle-distribution-sha256-sum 544c35d6bd849ae8a5ed0bcea39ba677dc40f49df7d1835561582da2009b961d
     - name: Fail groovy-dsl project
       working-directory: .github/workflow-samples/groovy-dsl
       continue-on-error: true

docs/wrapper-validation.md

@@ -111,7 +111,7 @@ we highly recommend that you reach out to us at [security@gradle.com](mailto:sec
 #### Unverifiable Wrapper Jars
 Wrapper Jars generated by Gradle versions `3.3` to `4.0` are not verifiable because those files were dynamically generated by Gradle in a non-reproducible way. It's not possible to verify the `gradle-wrapper.jar` for those versions are legitimate using a hash comparison. If you have a validation failure, you should try to determine if the `gradle-wrapper.jar` was generated by one of these versions before running the build.
 
-- If the Gradle version in `gradle-wrapper.properties` is outside of this range, you can regenerate the `gradle-wrapper.jar` by running `./gradlew wrapper`. This will generate a new, verifiable wrapper jar.
+- If the Gradle version in `gradle-wrapper.properties` is outside of this range, you can regenerate the `gradle-wrapper.jar` by running `./gradlew :wrapper`. This will generate a new, verifiable wrapper jar.
 - If you need to run your build with a version of Gradle between 3.3 and 4.0, you can use a newer version of Gradle to generate the `gradle-wrapper.jar`.
 
 #### Wrapper Jar stored with Git LFS