build: remove redundant maven-compiler testCompile execution

Tycho already compiles tests; the root POM's maven-compiler-plugin
execution (id: compiletests) caused a second javac pass.

Author: sebthom

pom.xml

@@ -191,20 +191,6 @@
 					</toolchains>
 				</configuration>
 			</plugin>
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-compiler-plugin</artifactId>
-				<version>3.14.1</version>
-				<executions>
-					<execution>
-						<id>compiletests</id>
-						<phase>test-compile</phase>
-						<goals>
-							<goal>testCompile</goal>
-						</goals>
-					</execution>
-				</executions>
-			</plugin>
 			<plugin>
 				<groupId>org.eclipse.tycho</groupId>
 				<artifactId>tycho-source-plugin</artifactId>