bump lombok to avoid java16+ compile error

[barryoneill]

On Java 16+, compilation fails with:

[error] Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private com.sun.tools.javac.processing.JavacProcessingEnvironment$DiscoveredProcessors com.sun.tools.javac.processing.JavacProcessingEnvironment.discoveredProcs accessible: module jdk.compiler does not "opens com.sun.tools.javac.processing" to unnamed module @7316cb78
[error] 	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
[error] 	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
[error] 	at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:180)
[error] 	at java.base/java.lang.reflect.Field.setAccessible(Field.java:174)
[error] 	at lombok.permit.Permit.setAccessible(Permit.java:50)
[error] 	at lombok.permit.Permit.getField(Permit.java:84)
[error] 	at lombok.javac.apt.LombokProcessor.getFieldAccessor(LombokProcessor.java:116)
[error] 	at lombok.javac.apt.LombokProcessor.<clinit>(LombokProcessor.java:110)

caused by projectlombok/lombok#2681

This PR upgrades lombok to a version containing the fix, and adds Java 18 to the build matrix.