CxxUtils: disable JetEvent in pedantic checkergcc build

The JetEvent package creates too many warnings in client packages. Disable checking of it in our special checkergcc build until we get around to fixing the thread-safety issues in it.

cc @ssnyder

Control/CxxUtils/share/checkergcc-pedantic.config

@@ -10,6 +10,8 @@
 [thread.check_paths]
 # Hack: disable checking of auto-generated Cint dictionaries:
 -CMakeFiles
+# JetEvent creates too many warnings in clients, disable it for now:
+-Reconstruction/Jet/JetEvent
 # Check all top-level source directories
 AsgExternal
 AtlasGeometryCommon