Accept Apache v2 and Protoc license headers

buildSrc/src/main/groovy/org/opensearch/gradle/precommit/LicenseHeadersTask.groovy

@@ -155,10 +155,16 @@ class LicenseHeadersTask extends AntTask {
         Map<String, LicenseSettings> licenseSettingsHashMap = new HashMap<>()
         Map<String, List<String>> licenseStats = new HashMap<>()
 
+        // Acceptable licenses by Apache Rat's defaults
+        // Apache 2
+        licenseSettingsHashMap.put("AL2", new LicenseSettings("AL", "Apache License Version 2.0", "Licensed to the Apache Software Foundation (ASF)"))
+        // Generate code from Protocol Buffer compiler
+        licenseSettingsHashMap.put("GENPROTOC", new LicenseSettings("GEN", "Generated", "Generated by the protocol buffer compiler.  DO NOT EDIT!"))
+
         // BSD 4-clause stuff (is disallowed below)
         // we keep this here, in case someone adds BSD code for some reason, it should never be allowed.
         licenseSettingsHashMap.put("BSD4", new LicenseSettings("BSD4", "Original BSD License (with advertising clause)", "All advertising materials"))
-        // Apache
+        // Apache (ES)
         licenseSettingsHashMap.put("AL", new LicenseSettings("AL", "Apache", "Licensed to Elasticsearch under one or more contributor"))
         // SPDX
         licenseSettingsHashMap.put("SPDX1", new LicenseSettings("SPDX", "SPDX", "SPDX-License-Identifier: Apache-2.0"))