[Integrated] RFR: Improve stripping of code blocks

[duke]

Changeset: 5d474ee4
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2019-09-24 09:15:31 +0000
URL:       https://git.openjdk.java.net/skara/commit/5d474ee4

Improve stripping of code blocks

Reviewed-by: ehelin

! bots/mlbridge/src/main/java/org/openjdk/skara/bots/mlbridge/MarkdownToText.java
! bots/mlbridge/src/test/java/org/openjdk/skara/bots/mlbridge/MarkdownToTextTests.java