Bump ajv from 6.12.1 to 6.12.6 in /docs

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.1 to 6.12.6.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](https://github.com/ajv-validator/ajv/compare/v6.12.1...v6.12.6)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/package-lock.json

@@ -11,15 +11,14 @@
       "dev": true
     },
     "ajv": {
-      "version": "6.12.1",
-      "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.12.1.tgz",
-      "integrity": "sha512-AUh2mDlJDAnzSRaKkMHopTD1GKwC1ApUq8oCzdjAOM5tavncgqWU+JoRu5Y3iYY0Q/euiU+1LWp0/O/QY8CcHw==",
+      "version": "6.12.6",
+      "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.12.6.tgz",
+      "integrity": "sha512-j3fVLgvTo527anyYyJOGTYJbG+vnnQYvE0m5mmkc1TK+nxAppkCLMIL0aZ4dblVCNoGShhm+kzE4ZUykBoMg4g==",
       "dev": true,
       "requires": {
         "fast-deep-equal": "^3.1.1",
         "fast-json-stable-stringify": "^2.0.0",
         "json-schema-traverse": "^0.4.1",
-        "opencollective-postinstall": "^2.0.2",
         "uri-js": "^4.2.2"
       }
     },
@@ -3703,12 +3702,6 @@
         "wrappy": "1"
       }
     },
-    "opencollective-postinstall": {
-      "version": "2.0.2",
-      "resolved": "https://registry.npmjs.org/opencollective-postinstall/-/opencollective-postinstall-2.0.2.tgz",
-      "integrity": "sha512-pVOEP16TrAO2/fjej1IdOyupJY8KDUM1CvsaScRbw6oddvpQoOfGk4ywha0HKKVAD6RkW4x6Q+tNBwhf3Bgpuw==",
-      "dev": true
-    },
     "ordered-read-streams": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/ordered-read-streams/-/ordered-read-streams-1.0.1.tgz",