[Bug] Replace trial/basic license to oss

Currenlty, /packages/osd-opensearch/README.md still uses trial/basic
license. This PR replaces them with oss and cleans the concepts.

Partially Resolved:
opensearch-project#592

Signed-off-by: Anan Zhuang <ananzh@amazon.com>

packages/osd-opensearch/README.md

@@ -9,9 +9,9 @@ To run, go to the OpenSearch Dashboards root and run `node scripts/opensearch --
 
 ### Examples
 
-Run a snapshot install with a trial license
+Run a snapshot install with an oss license
 ```
-node scripts/opensearch snapshot --license=trial
+node scripts/opensearch snapshot --license=oss
 ```
 
 Run from source with a configured data directory
@@ -26,8 +26,8 @@ Start a cluster
 ```
 var opensearch = require('@osd/opensearch');
 opensearch.run({
-  license: 'basic',
-  version: 7.0,
+  license: 'oss',
+  version: 1.0.0,
 })
 .catch(function (e) {
   console.error(e);
@@ -41,7 +41,7 @@ opensearch.run({
 
 Type: `String`
 
-License type, one of: trial, basic, gold, platinum
+License type, one of: oss, gold, platinum
 
 ##### options.version