Apply zig fmt to exercises

exercises/04_arrays.zig

@@ -46,6 +46,7 @@ pub fn main() void {
     // Use the len property to get the length of the array:
     const length = some_primes.???;
 
-    std.debug.print("First: {}, Fourth: {}, Length: {}\n",
-        .{first, fourth, length});
+    std.debug.print("First: {}, Fourth: {}, Length: {}\n", .{
+        first, fourth, length,
+    });
 }