bump Geant4 patch version

This small patch to Geant4 is helpful for biased production of samples in volumes upstream of the target and does not affect any of our current samples focused on production (biased or not) within the target or downstream volumes.

Dockerfile

@@ -239,7 +239,7 @@ ENV CLING_STANDARD_PCH=none
 # Assumptions
 #  - GEANT4 defined to be a release of geant4 or LDMX's fork of geant4
 ###############################################################################
-ENV GEANT4=LDMX.10.2.3_v0.5
+ENV GEANT4=LDMX.10.2.3_v0.6
 ENV G4DATADIR="${__prefix}/share/geant4/data"
 LABEL geant4.version="${GEANT4}"
 RUN __owner="geant4" &&\