Remove IMDG from search-config.json (#475)

# Description of change

IMDG is unsupported and search is disabled for /imdg - let's remove from
index to save effort and credits.

## Type of change

Select the type of change that you're making:

- [ ] Bug fix (Addresses an issue in existing content such as a typo)
- [x] Enhancement (Adds new content)

Author: oliverhowell

search-config.json

@@ -8,18 +8,6 @@
       ],
       "selectors_key": "tutorials"
     },
-    {
-      "url": "https://docs.hazelcast.com/imdg/(?P<version>.*?)/",
-      "tags": [
-        "imdg-4.2"
-      ],
-      "variables": {
-        "version": [
-          "4.2"
-        ]
-      },
-      "selectors_key": "imdg"
-    },
     {
       "url": "https://docs.hazelcast.com/management-center/(?P<version>.*?)/",
       "tags": [
@@ -496,24 +484,6 @@
       "lvl3": ".doc h2",
       "text": ".doc p, .doc td.content, .doc th.tableblock"
     },
-    "imdg": {
-      "lvl0": {
-        "selector": "/html[1]/body[1]/div[1]/main[1]/div[1]/nav[1]/ul[1]/li[1]/a[1]",
-        "type": "xpath",
-        "global": true,
-        "default_value": "IMDG"
-      },
-      "lvl1": {
-        "selector": "/html[1]/body[1]/div[1]/main[1]/div[1]/nav[1]/ul[1]/li[2]/a[1]",
-        "type": "xpath",
-        "global": true
-      },
-      "lvl2": ".doc h1",
-      "lvl3": ".doc h2",
-      "lvl4": ".doc h3",
-      "lvl5": ".doc h4",
-      "text": ".doc p, .doc td.content, .doc th.tableblock"
-    },
     "mc": {
       "lvl0": {
         "selector": "/html[1]/body[1]/div[1]/main[1]/div[1]/article[1]/nav[1]/ul[1]/li[1]/a[1]",