Remove references to FS Shard check from the docs

These checks were a no op on Cloud native environments, and the checks
were migrated as part of:
https://gitlab.com/gitlab-org/gitaly/merge_requests/767

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/49725

doc/user/admin_area/monitoring/health_check.md

@@ -42,12 +42,6 @@ Readiness example output:
    "shared_state_check" : {
       "status" : "ok"
    },
-   "fs_shards_check" : {
-      "labels" : {
-         "shard" : "default"
-      },
-      "status" : "ok"
-   },
    "db_check" : {
       "status" : "ok"
    },
@@ -61,9 +55,6 @@ Liveness example output:
 
 ```
 {
-   "fs_shards_check" : {
-      "status" : "ok"
-   },
    "cache_check" : {
       "status" : "ok"
    },