safe delete: do not insert additional extends item if already present (IDEA-106144)

java/java-tests/testData/refactoring/safeDelete/UsageInExtendsList.java

@@ -0,0 +1,3 @@
+nterface Foo {}
+interface Ba<caret>r extends Foo {}
+class FooBarImpl implements Foo, Bar {}

java/java-tests/testData/refactoring/safeDelete/UsageInExtendsList_after.java

@@ -0,0 +1,3 @@
+nterface Foo {}
+
+class FooBarImpl implements Foo {}