Remove license header check files

These look like they were used with an older license header check. I suspect
these are obsolete.

dev-tools/src/main/resources/license-check/elasticsearch_license_header.txt

@@ -1,16 +0,0 @@
-Licensed to Elasticsearch under one or more contributor
-license agreements. See the NOTICE file distributed with
-this work for additional information regarding copyright
-ownership. Elasticsearch licenses this file to you 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.

dev-tools/src/main/resources/license-check/license_header_definition.xml

@@ -1,13 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<additionalHeaders>
-    <javadoc_style>
-        <firstLine>/*</firstLine>
-        <beforeEachLine> * </beforeEachLine>
-        <endLine> */</endLine>
-        <!--skipLine></skipLine-->
-        <firstLineDetectionPattern>(\s|\t)*/\*.*$</firstLineDetectionPattern>
-        <lastLineDetectionPattern>.*\*/(\s|\t)*$</lastLineDetectionPattern>
-        <allowBlankLines>false</allowBlankLines>
-        <isMultiline>true</isMultiline>
-    </javadoc_style>
-</additionalHeaders>