pom: remove source/target configuration on maven-compiler-plugin

On Java 11, which we require for building, the compiler accepts
--release 8 and no longer requires -source or -target, so these are
unnecessary

http-service/pom.xml

@@ -167,6 +167,8 @@
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
 				<configuration>
+					<source>1.8</source> <!-- required for mapstruct -->
+					<target>1.8</target> <!-- required for mapstruct -->
 					<annotationProcessorPaths>
 						<path>
 							<groupId>org.mapstruct</groupId>

pom.xml

@@ -38,7 +38,6 @@
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.build.outputTimestamp>1</project.build.outputTimestamp>
-		<java.version>1.8</java.version>
 		<java.release>8</java.release>
 		<lombok.version>1.18.20</lombok.version>
 
@@ -183,8 +182,6 @@
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
 				<configuration>
-					<source>${java.version}</source>
-					<target>${java.version}</target>
 					<release>${java.release}</release>
 				</configuration>
 			</plugin>

runelite-jshell/pom.xml

@@ -73,8 +73,6 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <configuration>
-                    <source>11</source>
-                    <target>11</target>
                     <release>11</release>
                 </configuration>
             </plugin>