Fix the compiler message in a code example in docs

Author: ShapelessCat

docs/docs/reference/other-new-features/safe-initialization.md

@@ -29,7 +29,7 @@ The checker will report:
 
 ``` scala
 -- Warning: tests/init/neg/AbstractFile.scala:7:4 ------------------------------
-7 |	val localFile: String = url.hashCode + ".tmp"  // error
+7 |	val localFile: String = s"${url.##}.tmp"  // error: usage of `localFile` before it's initialized
   |	    ^
   |    Access non-initialized field value localFile. Calling trace:
   |     -> val extension: String = name.substring(4)	[ AbstractFile.scala:3 ]
@@ -183,7 +183,6 @@ are transitively initialized, so is the result.
 
 With the established principles and design goals, following rules are imposed:
 
-
 1. In an assignment `o.x = e`, the expression `e` may only point to transitively initialized objects.
 
    This is how monotonicity is enforced in the system. Note that in an