Remove IBM copyright

This copyright isn't needed and is not in any other file.
It is not being updated. Just remove it.

Similar changes were done at
https://gerrit.openbmc.org/c/openbmc/bmcweb/+/41139.

This was added in the original commit of this repo:
https://github.com/openbmc/phosphor-user-manager/commit/8a89b53bf014d0844dfd85b2327853037d1e2cb7

Tested: None. Document change only.

Change-Id: Ifc9f73a430af8c5da6174e4c48b318b1bbc41ee5
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/mainapp.cpp b/mainapp.cpp
index fa5f9f6..b54e2cb 100644
--- a/mainapp.cpp
+++ b/mainapp.cpp
@@ -1,18 +1,3 @@
-/**
- * Copyright © 2016 IBM Corporation
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
 #include "config.h"
 
 #include "user_mgr.hpp"