[lldb][docs] Remove syntax hint from some output blocks
This tries to parse the block as that language but in these
cases fails because they aren't purely that language. This
falls back to a permissive mode which is fine, but highlights
the invalid tokens like errors which isn't great.
Instead don't try to highlight these blocks. This fixes 4
warnings seen in the docs build:
lldb/docs/use/tutorials/custom-frame-recognizers.md:43: WARNING: Lexing literal_block <...> as "c++" resulted in an error at token: '#'. Retrying in relaxed mode.
lldb/docs/use/tutorials/script-driven-debugging.md:175: WARNING: Lexing literal_block <...> as "c++" resulted in an error at token: '#'. Retrying in relaxed mode.
lldb/docs/use/tutorials/script-driven-debugging.md:426: WARNING: Lexing literal_block <...> as "c++" resulted in an error at token: '#'. Retrying in relaxed mode.
lldb/docs/use/tutorials/writing-custom-commands.md:416: WARNING: Lexing literal_block <...> as "python3" resulted in an error at token: '$'. Retrying in relaxed mode.
