Ignore generated-sources in coverage reports

- We don't test it directly, nor is it our job
 - A bad grammar won't be processed, or fail in subtle ways only
   detectable in specific tests on the AST (which is included)

pom.xml

@@ -612,6 +612,11 @@
                     <groupId>org.jacoco</groupId>
                     <artifactId>jacoco-maven-plugin</artifactId>
                     <version>0.8.11</version>
+                    <configuration>
+                        <excludes>
+                            <exclude>**/target/generated-sources/**</exclude>
+                        </excludes>
+                    </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.cyclonedx</groupId>