fix method signature

(previous version also lacked the invocant marker but happened to compile)

Author: coke

doc/Type/Array.pod6

@@ -205,8 +205,8 @@ Example:
 
 Defined as:
 
-    multi sub    splice(@list,  $start = 0, $elems?, *@replacement --> Array)
-    multi method splice(Array:D $start = 0, $elems?, *@replacement --> Array)
+    multi sub    splice(@list,   $start = 0, $elems?, *@replacement --> Array)
+    multi method splice(Array:D: $start = 0, $elems?, *@replacement --> Array)
 
 Deletes C<$elems> elements starting from index C<$start> from the C<Array>,
 returns them and replaces them by C<@replacement>. If C<$elems> is omitted,