JarScanner: Use ASM7 opcodes

This avoids a runtime error when visiting bytecode that uses opcodes
new in Java 11.

Change-Id: I33e1f34ee288c347d1f4ceb436c5dec2ad0a5907
diff --git a/java/com/google/gerrit/server/plugins/JarScanner.java b/java/com/google/gerrit/server/plugins/JarScanner.java
index 1a9b859..486e264 100644
--- a/java/com/google/gerrit/server/plugins/JarScanner.java
+++ b/java/com/google/gerrit/server/plugins/JarScanner.java
@@ -195,7 +195,7 @@
     Collection<String> exports;
 
     private ClassData(Collection<String> exports) {
-      super(Opcodes.ASM6);
+      super(Opcodes.ASM7);
       this.exports = exports;
     }
 
@@ -263,7 +263,7 @@
 
   private abstract static class AbstractAnnotationVisitor extends AnnotationVisitor {
     AbstractAnnotationVisitor() {
-      super(Opcodes.ASM6);
+      super(Opcodes.ASM7);
     }
 
     @Override