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

* Update to latest @actions/core version

* Bump release notes for new versions

* Add correct pr #

RELEASES.md

@@ -41,3 +41,8 @@
 ### 0.4.0
 
 - Add option to specify custom retentions on artifacts
+
+### 0.4.1
+
+- Update to latest @actions/core version
+

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/artifact",
-  "version": "0.4.0",
+  "version": "0.4.1",
   "preview": true,
   "description": "Actions artifact lib",
   "keywords": [
@@ -37,7 +37,7 @@
     "url": "https://github.com/actions/toolkit/issues"
   },
   "dependencies": {
-    "@actions/core": "^1.2.1",
+    "@actions/core": "^1.2.6",
     "@actions/http-client": "^1.0.7",
     "@types/tmp": "^0.1.0",
     "tmp": "^0.1.0",