Improve meeting ended by user dialog box to indicate who ended the meeting.

[ritzalam]

Describe the bug
When a moderator ends the meeting, the dialog displays the session has ended in bold letters while at the bottom it says the meeting ended by "name of user".

Unfortunately, users just read the bold text and not the rest of the texts.

To Reproduce
Steps to reproduce the behavior:

1. Have to mods join the meeting.
2. One mod ends the meeting when logging out.
3. Read the end meeting dialog.
4. The dialog has the bolded "This session has ended"

Expected behavior
Change the bolded text to read "This session was ended by Karen".

Actual behavior
See screenshot below.

Screenshots

BBB version (optional):
BigBlueButton Server 2.3

Additional context
See issue #9856

[antobinary]

Implemented in #12519