[FIR] Fix TEST SPEC tests

Ensure the test data contents for both the frontends
are identical. This is needed for proper analysis of
K2-differences.

compiler/tests-spec/testData/diagnostics/linked/expressions/elvis-operator-expression/p-3/pos/1.1.fir.kt

@@ -1,6 +1,17 @@
 // !DIAGNOSTICS: -UNREACHABLE_CODE -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION
 // SKIP_TXT
 
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
+ *
+ * SPEC VERSION: 0.1-218
+ * MAIN LINK: expressions, elvis-operator-expression -> paragraph 3 -> sentence 1
+ * NUMBER: 1
+ * DESCRIPTION: The type of elvis operator expression is the least upper bound of the non-nullable variant of the type of the left-hand side expression and the type of the right-hand side expression.
+ * HELPERS: checkType
+ */
+
+
 // TESTCASE NUMBER: 1
 fun case1() {
     val x = null ?: getNull()