Wording of default message in quick outline

[jrieken]

re #93643

• trigger quick outline where it cannot be triggered
• see the message below, the last part reads weird

How about

• The active text editor does not provide [symbols|symbol information|outline information]
• To go to a symbol, open a text editor with symbol information first

[gjsjohnmurray]

* To go to a symbol, open a text editor with symbol information first

If this option is preferred I suggest a slight variation:

• To go to a symbol, first open a text editor with symbol information.

[bpasero]

We actually need 2 messages:

• no editor or no text editor open
• text editor open but no symbol information

I went with:

• To go to a symbol, first open a text editor with symbol information.
• The active text editor does not provide symbol information.

[hamaney]

I find the new message missing some directions to where/how to provide some symbol information. Finally I figure out that I have to enable the c/cpp extension for the workspace.