refactor(core): simplify language setter in CodePartEditorInfo

Remove redundant `setLanguage` call and directly assign value to `file.language

Author: phodal

core/src/main/kotlin/com/intellij/temporary/gui/block/CodePartEditorInfo.kt

@@ -16,6 +16,6 @@ class CodePartEditorInfo(
     var language: Language
         get() = file.language
         set(value) {
-            file.setLanguage(value)
+            file.language = value
         }
 }