SLING-7828 - Generating adapter metadata fails when using Java 8 features: invalid constant type: 18

Use a more recent version of javassist. The exclusion is needed since
javassist has changed Maven coordinates in the meantime.
diff --git a/pom.xml b/pom.xml
index 6d66d17..7b98a21 100644
--- a/pom.xml
+++ b/pom.xml
@@ -211,6 +211,17 @@
             <groupId>net.sf.scannotation</groupId>
             <artifactId>scannotation</artifactId>
             <version>1.0.2</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>javassist</groupId>
+                    <artifactId>javassist</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>org.javassist</groupId>
+            <artifactId>javassist</artifactId>
+            <version>3.18.2-GA</version>
         </dependency>
         <dependency>
             <groupId>org.apache.sling</groupId>