Add missing dependency

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

jsonnetfile.json

 {
   "version": 1,
   "dependencies": [
+    {
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs.git",
+          "subdir": "mixin-utils"
+        }
+      },
+      "version": "master"
+    },
     {
       "source": {
         "local": {

jsonnetfile.lock.json

@@ -91,6 +91,16 @@
       "version": "db0e776c0bc76766f29580be3eb6f3b317486c48",
       "sum": "+z5VY+bPBNqXcmNAV8xbJcbsRA+pro1R3IM7aIY8OlU="
     },
+    {
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs.git",
+          "subdir": "mixin-utils"
+        }
+      },
+      "version": "cee0123922f4877b37804d95f3ee2c975a66b31e",
+      "sum": "wi1o6t5nUZVcsatqMdGLOWIv1HxNnlaE84oRE0Cl0ec="
+    },
     {
       "source": {
         "git": {