feat: use github.com/eic/eic-spack as local eic-spack repo

Instead of using the local eic-spack repo, we should use the github eic-spack repo. That centralizes and makes it easier for users to use the same package recipes.

.gitlab-ci.yml

@@ -17,7 +17,7 @@ variables:
   ## 5bd44a795c76a61f0f9fbfeedcf7e917a0bf40b0: lcio, podio, edm4hep: add latest versions
 
   ## Spack github version, e.g. v0.18 or commit hash
-  EICSPACK_VERSION: "v0.18.0"
+  EICSPACK_VERSION: "d7606f67a36708dcc0c045a269621f4189345aad"
   ## Space-separated list of eic=spack cherry-picks
   EICSPACK_CHERRYPICKS: ""