fix(panel): Documentation/comment refactoring

[bradrich]

Actual Behavior:

• What is the issue? * There are several documentation / comment lines in the mdPanel service that are not following the correct syntax.
• What is the expected behavior? These syntax requirements are important to the understanding of the mdPanel service API and the documentation / comment lines need to be adjusted to comply.

CodePen (or steps to reproduce the issue): *

• CodePen Demo which shows your issue: N/A
• Details: N/A

Angular Versions: *

• Angular Version: Latest
• Angular Material Version: Latest

Additional Information:

• Browser Type: * N/A
• Browser Version: * N/A
• OS: * N/A
• Stack Traces: N/A

Ping @ErinCoughlan

[topherfangio]

@bradrich Just saw this. Might be fixed by #9360?

[bradrich]

@topherfangio I am not sure about the incorrect Markdown support in the panel docs. I wasn't aware of that issue. My fix is based on incorrect usage of some of the documentation definitions. I am sure that our fixes could work together.