Fix test on unused import suppression

Before the fix for KT-7185, the file looked like:
package suppression
@file:Suppress("UnusedImport")

import java.io.* // unused

And it was parsed incorrectly, because @file: annotations
should come before package directive
But after fix, import directives started being parsed that lead
to wrong unused import (because suppression wasn't parsed still)

idea/testData/inspections/unusedImport/suppression.kt

@@ -1,3 +1,4 @@
 @file:Suppress("UnusedImport")
+package suppression
 
-import java.io.* // unused
+import java.io.* // unused

idea/tests/org/jetbrains/kotlin/idea/codeInsight/AbstractInspectionTest.kt

@@ -94,7 +94,7 @@ abstract class AbstractInspectionTest : KotlinLightCodeInsightFixtureTestCase()
                     file.extension == "kt" -> {
                         val text = FileUtil.loadFile(file, true)
                         val fileText =
-                            if (text.startsWith("package"))
+                            if (text.lines().any { it.startsWith("package") })
                                 text
                             else
                                 "package ${file.nameWithoutExtension};$text"