Use packages.matrix.org for Olm

Fixes https://github.com/vector-im/riot-web/issues/9497

package.json

@@ -76,7 +76,7 @@
     "matrix-js-sdk": "1.0.4",
     "matrix-react-sdk": "1.0.7",
     "modernizr": "^3.6.0",
-    "olm": "https://matrix.org/packages/npm/olm/olm-3.1.0-pre3.tgz",
+    "olm": "https://packages.matrix.org/npm/olm/olm-3.1.0-pre3.tgz",
     "prop-types": "^15.6.2",
     "react": "^15.6.0",
     "react-dom": "^15.6.0",

yarn.lock

@@ -6383,9 +6383,9 @@ obuf@^1.0.0, obuf@^1.1.2:
   resolved "https://registry.yarnpkg.com/obuf/-/obuf-1.1.2.tgz#09bea3343d41859ebd446292d11c9d4db619084e"
   integrity sha512-PX1wu0AmAdPqOL1mWhqmlOd8kOIZQwGZw6rh7uby9fTc5lhaOWFLX3I6R1hrF9k3zUY40e6igsLGkDXK92LJNg==
 
-"olm@https://matrix.org/packages/npm/olm/olm-3.1.0-pre3.tgz":
+"olm@https://packages.matrix.org/npm/olm/olm-3.1.0-pre3.tgz":
   version "3.1.0-pre3"
-  resolved "https://matrix.org/packages/npm/olm/olm-3.1.0-pre3.tgz#525aa8191b4b6fcb07a3aa6815687780b99be411"
+  resolved "https://packages.matrix.org/npm/olm/olm-3.1.0-pre3.tgz#525aa8191b4b6fcb07a3aa6815687780b99be411"
 
 on-finished@~2.3.0:
   version "2.3.0"