Move Sonar plugin dependency to POM plugin management

This is needed to allow Dependabot to detect plugin upgrades.

.github/workflows/main.yml

@@ -48,8 +48,7 @@ jobs:
           restore-keys: ${{ runner.os }}-maven
       - name: Test with Sonar
         run: >
-          ./mvnw -V --no-transfer-progress -e clean verify javadoc:javadoc
-          org.sonarsource.scanner.maven:sonar-maven-plugin:3.8.0.2131:sonar
+          ./mvnw -V --no-transfer-progress -e clean verify javadoc:javadoc sonar:sonar
           -Dsonar.host.url=https://sonarcloud.io
           -Dsonar.organization=assertj
           -Dsonar.projectKey=joel-costigliola_assertj-core

pom.xml

@@ -634,6 +634,11 @@
     </plugins>
     <pluginManagement>
       <plugins>
+        <plugin>
+          <groupId>org.sonarsource.scanner.maven</groupId>
+          <artifactId>sonar-maven-plugin</artifactId>
+          <version>3.9.0.2155</version>
+        </plugin>
         <plugin>
           <groupId>net.alchim31.maven</groupId>
           <artifactId>yuicompressor-maven-plugin</artifactId>