add trailing newlines to test files

otherwise I have to rollback dozens of files after using sed that follows conventions

compiler/testData/diagnostics/tests/shadowing/ShadowParameterInFunctionBody.jet

@@ -1,4 +1,4 @@
 fun f(<!UNUSED_PARAMETER!>p<!>: Int): Int {
     val <!NAME_SHADOWING!>p<!> = 2
     return p
-}
+}

compiler/testData/diagnostics/tests/shadowing/ShadowParameterInNestedBlockInFor.jet

@@ -4,4 +4,4 @@ fun f(<!UNUSED_PARAMETER!>i<!>: Int) {
             var <!NAME_SHADOWING!>i<!> = 12
         }<!>
     }
-}
+}

compiler/testData/diagnostics/tests/shadowing/ShadowVariableInNestedBlock.jet

@@ -4,4 +4,4 @@ fun ff(): Int {
         val <!NAME_SHADOWING!>i<!> = 2
     }<!>
     return i
-}
+}

compiler/testData/diagnostics/tests/shadowing/ShadowVariableInNestedClosure.jet

@@ -2,4 +2,4 @@ fun f(): Int {
     var i = 17
     <!UNUSED_FUNCTION_LITERAL!>{ (): Unit -> var <!NAME_SHADOWING!>i<!> = 18 }<!>
     return i
-}
+}

compiler/testData/diagnostics/tests/shadowing/ShadowVariableInNestedClosureParam.jet

@@ -2,4 +2,4 @@ fun ff(): Int {
     var i = 1
     <!UNUSED_FUNCTION_LITERAL!>{ (i: Int) -> i }<!>
     return i
-}
+}