fix type parameter migration for extension functions

idea/testData/quickfix/migration/typeParameterList/extension.kt

@@ -0,0 +1,5 @@
+// "Migrate type parameter list syntax" "true"
+
+class Foo
+
+fun Foo.f<caret><T>() {}

idea/testData/quickfix/migration/typeParameterList/extension.kt.after

@@ -0,0 +1,5 @@
+// "Migrate type parameter list syntax" "true"
+
+class Foo
+
+fun <T> Foo.f() {}