Update ajv to the latest version 🚀 (ampproject#13150)

* chore(package): update ajv to version 6.1.1

* chore(package): update lockfile

https://npm.im/greenkeeper-lockfile

package.json

@@ -42,7 +42,7 @@
   },
   "devDependencies": {
     "acorn-globals": "4.1.0",
-    "ajv": "5.5.2",
+    "ajv": "6.1.1",
     "ajv-keywords": "2.1.1",
     "ansi-colors": "1.0.1",
     "ast-replace": "1.1.3",

yarn.lock

@@ -247,11 +247,10 @@ ajv-keywords@2.1.1, ajv-keywords@^2.1.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-2.1.1.tgz#617997fc5f60576894c435f940d819e135b80762"
 
-ajv@5.5.2, ajv@^5.1.0, ajv@^5.2.3, ajv@^5.3.0:
-  version "5.5.2"
-  resolved "https://registry.yarnpkg.com/ajv/-/ajv-5.5.2.tgz#73b5eeca3fab653e3d3f9422b341ad42205dc965"
+ajv@6.1.1:
+  version "6.1.1"
+  resolved "https://registry.yarnpkg.com/ajv/-/ajv-6.1.1.tgz#978d597fbc2b7d0e5a5c3ddeb149a682f2abfa0e"
   dependencies:
-    co "^4.6.0"
     fast-deep-equal "^1.0.0"
     fast-json-stable-stringify "^2.0.0"
     json-schema-traverse "^0.3.0"
@@ -263,6 +262,15 @@ ajv@^4.9.1:
     co "^4.6.0"
     json-stable-stringify "^1.0.1"
 
+ajv@^5.1.0, ajv@^5.2.3, ajv@^5.3.0:
+  version "5.5.2"
+  resolved "https://registry.yarnpkg.com/ajv/-/ajv-5.5.2.tgz#73b5eeca3fab653e3d3f9422b341ad42205dc965"
+  dependencies:
+    co "^4.6.0"
+    fast-deep-equal "^1.0.0"
+    fast-json-stable-stringify "^2.0.0"
+    json-schema-traverse "^0.3.0"
+
 align-text@^0.1.1, align-text@^0.1.3:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/align-text/-/align-text-0.1.4.tgz#0cd90a561093f35d0a99256c22b7069433fad117"