Remove version and snapshots from readme (#25747)

So long as we are referencing the version of Kibana in our readme, we
cannot reliably automate the bumping of the Kibana version as part of
our release process.

None of the other repos in the stack include version information or
links to snapshots in the readme. If folks want to know what version
they're looking at, the package.json is the source of truth.

README.md

@@ -1,4 +1,4 @@
-# Kibana 6.3.3
+# Kibana
 
 Kibana is your window into the [Elastic Stack](https://www.elastic.co/products). Specifically, it's a browser-based analytics and search dashboard for Elasticsearch.
 
@@ -37,16 +37,6 @@ out an open PR:
 - For all other questions, check out the [FAQ.md](FAQ.md) and
 [wiki](https://github.com/elastic/kibana/wiki).
 
-### Snapshot Builds
-
-For the daring, snapshot builds are available. These builds are created nightly and have undergone no formal QA, so they should never be run in production. All builds are 64 bit.
-
-| platform | default | OSS |
-| --- | --- | --- |
-| OSX | [tar](https://snapshots.elastic.co/downloads/kibana/kibana-6.3.3-SNAPSHOT-darwin-x86_64.tar.gz) | [tar](https://snapshots.elastic.co/downloads/kibana/kibana-oss-6.3.3-SNAPSHOT-darwin-x86_64.tar.gz) |
-| Linux | [tar](https://snapshots.elastic.co/downloads/kibana/kibana-6.3.3-SNAPSHOT-linux-x86_64.tar.gz) [deb](https://snapshots.elastic.co/downloads/kibana/kibana-6.3.3-SNAPSHOT-amd64.deb) [rpm](https://snapshots.elastic.co/downloads/kibana/kibana-6.3.3-SNAPSHOT-x86_64.rpm) | [tar](https://snapshots.elastic.co/downloads/kibana/kibana-oss-6.3.3-SNAPSHOT-linux-x86_64.tar.gz) [deb](https://snapshots.elastic.co/downloads/kibana/kibana-oss-6.3.3-SNAPSHOT-amd64.deb) [rpm](https://snapshots.elastic.co/downloads/kibana/kibana-oss-6.3.3-SNAPSHOT-x86_64.rpm) |
-| Windows | [zip](https://snapshots.elastic.co/downloads/kibana/kibana-6.3.3-SNAPSHOT-windows-x86_64.zip) | [zip](https://snapshots.elastic.co/downloads/kibana/kibana-oss-6.3.3-SNAPSHOT-windows-x86_64.zip) |
-
 ## Documentation
 
 Visit [Elastic.co](http://www.elastic.co/guide/en/kibana/current/index.html) for the full Kibana documentation.