Fix check file for i18678b

Author: ausmarton

tests/neg/i18678b.check

@@ -1,4 +1,4 @@
--- [E007] Type Mismatch Error: tests/neg/i18678b.scala:3:16 --------------------
+-- [E007] Type Mismatch Error: tests/neg/i18678b.scala:3:16 ------------------------------------------------------------
 3 |def s: String = "" // error
   |                ^^
   |                Found:    ("" : String)
@@ -7,4 +7,4 @@
   |                where:    String  is a class in package java.lang
   |                          String² is a class in the empty package
   |
-  | longer explanation available when compiling with `-explain`
+  | longer explanation available when compiling with `-explain`