[FLINK-36181] Bump Scala to 2.12.19

This is a breaking change for Flink 2.0, and allows us to next remove the specific Scala versions for both Java 17 and 21

pom.xml

@@ -138,9 +138,7 @@ under the License.
 		<maven.compiler.source>${target.java.version}</maven.compiler.source>
 		<maven.compiler.target>${target.java.version}</maven.compiler.target>
 		<scala.macros.version>2.1.1</scala.macros.version>
-		<!-- Default scala versions, must be overwritten by build profiles, so we set something
-		invalid here -->
-		<scala.version>2.12.7</scala.version>
+		<scala.version>2.12.19</scala.version>
 		<scala.binary.version>2.12</scala.binary.version>
 		<chill.version>0.7.6</chill.version>
 		<!-- keep FlinkTestcontainersConfigurator.configureZookeeperContainer in sync -->
@@ -973,7 +971,7 @@ under the License.
 		<profile>
 			<id>scala-2.12</id>
 			<properties>
-				<scala.version>2.12.7</scala.version>
+				<scala.version>2.12.19</scala.version>
 				<scala.binary.version>2.12</scala.binary.version>
 			</properties>
 			<activation>