Fix inconsistent Python union creator function naming (#8981)

tests/union_name_test/my_test_union.py

@@ -0,0 +1,20 @@
+# automatically generated by the FlatBuffers compiler, do not modify
+
+# namespace: union_name_test
+
+class my_test_union(object):
+    NONE = 0
+    Foo = 1
+    Bar = 2
+
+def MyTestUnionCreator(unionType, table):
+    from flatbuffers.table import Table
+    if not isinstance(table, Table):
+        return None
+    if unionType == my_test_union.Foo:
+        import union_name_test.Foo
+        return union_name_test.Foo.FooT.InitFromBuf(table.Bytes, table.Pos)
+    if unionType == my_test_union.Bar:
+        import union_name_test.Bar
+        return union_name_test.Bar.BarT.InitFromBuf(table.Bytes, table.Pos)
+    return None