Revert "chore: edm4eic 6.0.0"

This reverts commit 513cc448.

This commit went into master instead of a PR by mistake. The current
EICrecon was not forward-compatible with EDM4eic 6.0.0. Reverting to get
back to a valid state.

eic-spack.sh

@@ -3,7 +3,7 @@ EICSPACK_ORGREPO="eic/eic-spack"
 
 ## EIC spack commit hash or github version, e.g. v0.19.7
 ## note: nightly builds could use a branch e.g. releases/v0.19
-EICSPACK_VERSION="ad33251135b154690a0bf408e81dda293a0097e0"
+EICSPACK_VERSION="c0da90347ee66d2744fcee905d8e49e58a639782"
 
 ## Space-separated list of eic-spack cherry-picks
 read -r -d '' EICSPACK_CHERRYPICKS <<- \

spack-environment/packages.yaml

@@ -84,7 +84,7 @@ packages:
     - '@656aa3192b097a631ddd1e0380e80c26fd6644a7'
   edm4eic:
     require:
-    - '@6.0.0' # EDM4EIC_VERSION
+    - '@5.0.0' # EDM4EIC_VERSION
     - cxxstd=20
   edm4hep:
     require: