Minor, remove obsolete directives from jvm-abi-gen tests

Language version 1.6 was needed in these tests to enable annotation
instantiation, but that feature is now enabled by default.

plugins/jvm-abi-gen/test/org/jetbrains/kotlin/jvm/abi/BaseJvmAbiTest.kt

@@ -83,10 +83,6 @@ abstract class BaseJvmAbiTest : TestCase() {
             ).toTypedArray()
             destination = compilation.destinationDir.canonicalPath
             useOldBackend = !useIrBackend
-            languageVersion =
-                if (directives != null)
-                    InTextDirectivesUtils.findStringWithPrefixes(directives, "// LANGUAGE_VERSION:")
-                else null
             noSourceDebugExtension =
                 directives != null && InTextDirectivesUtils.findStringWithPrefixes(directives, "// NO_SOURCE_DEBUG_EXTENSION") != null
         }

plugins/jvm-abi-gen/testData/compile/inlineAnnotationInstantiation/directives.txt

@@ -1,3 +1,2 @@
-// LANGUAGE_VERSION: 1.6
 // IGNORE_BACKEND_LEGACY: JVM
-// IGNORE_BACKEND: JVM
+// IGNORE_BACKEND: JVM

plugins/jvm-abi-gen/testData/content/annotationInstantiation/directives.txt

@@ -1,3 +1,2 @@
-// LANGUAGE_VERSION: 1.6
 // IGNORE_BACKEND_LEGACY: JVM
-// IGNORE_BACKEND: JVM
+// IGNORE_BACKEND: JVM

plugins/jvm-abi-gen/testData/content/anonymousAnnotationInstantiation/directives.txt

@@ -1,3 +1,2 @@
-// LANGUAGE_VERSION: 1.6
 // IGNORE_BACKEND_LEGACY: JVM
 // IGNORE_BACKEND: JVM