Excessive whitespace around unsorted lists in attachment data values

Description:

When using markdown to provide an unsorted list inside a data value in an attachment through the postMessage API, there is an excessively large area of whitespace above and below the list.

Steps to reproduce:

1. Use an API client to send a message that includes a data item with the key "Some key" and the value "* Some text"

Expected behavior:

There is no additional whitespace above what would be seen for a plain text data value

Actual behavior:

Server Setup Information:

• Version of Rocket.Chat Server: 3.14.0
• Operating System: Linux (variant unknown, managed by Azure AKS)
• Deployment Method: Helm 3
• Number of Running Instances: 1
• DB Replicaset Oplog: Enabled
• NodeJS Version: v12.22.1
• MongoDB Version: 4.4.5

Client Setup Information

• Desktop App or Browser Version: Chrome Version 89.0.4389.114 (Official Build)
• Operating System: MacOS 11.3

Additional context

N/A

Relevant logs:

N/A

Start by reproducing the issue with an API client using the postMessage API and an attachment data value containing "* Some text". Trace how markdown lists in attachment values are rendered, then verify that the list has no excess whitespace compared with a plain-text data value.