Update @actions/core in remaining toolkit packages (#636)

* Update to latest @actions/core version

* Bump release notes for new versions

* Add correct pr #

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/tool-cache",
-  "version": "1.6.0",
+  "version": "1.6.1",
   "description": "Actions tool-cache lib",
   "keywords": [
     "github",
@@ -36,7 +36,7 @@
     "url": "https://github.com/actions/toolkit/issues"
   },
   "dependencies": {
-    "@actions/core": "^1.2.3",
+    "@actions/core": "^1.2.6",
     "@actions/exec": "^1.0.0",
     "@actions/http-client": "^1.0.8",
     "@actions/io": "^1.0.1",