eliuds-eggs: format config.json (#2158)

Running `mise run update-exercise --slug eliuds-eggs` will format the
config file in this way.

Author: senekor

exercises/practice/eliuds-eggs/.meta/config.json

@@ -1,5 +1,7 @@
 {
-  "authors": ["senekor"],
+  "authors": [
+    "senekor"
+  ],
   "files": {
     "solution": [
       "src/lib.rs",