Remove HIE_CACHE from cache key (#2050)

This was added in haskell/haskell-ide-engine#968 (comment)
I think it is better to make explicit the invalidation with a commit, to make clear in the commit history when it was done

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.circleci/config.yml

@@ -14,7 +14,7 @@ defaults: &defaults
 
     - restore_cache:
         keys:
-          - v4-stack-cache-{{ .Environment.HIE_CACHE }}-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "resolver.txt" }}
+          - v4-stack-cache-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "resolver.txt" }}
 
     - run:
         name: Stack upgrade
@@ -40,7 +40,7 @@ defaults: &defaults
         destination: bin
 
     - save_cache:
-        key: v4-stack-cache-{{ .Environment.HIE_CACHE }}-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "resolver.txt" }}
+        key: v4-stack-cache-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "resolver.txt" }}
         paths: &cache_paths
           - ~/.stack