docs: Update instructions for debugging LSP (#39527)

docs: update instructions for debugging LSP

Previously, it was suggested to set:

    vim.lsp.log.set_format_func(vim.inspect)

This made sense before f72c13341afb3e2459202d3f6e57cd00614c2ab5, when
`format_func` was called once per argument being logged, but since that
commit it's called with the log level followed by the other args, so the
suggested setting would call `vim.inspect(log_level, ....)` which would
just print the human readable name of the current log level and no other
details, for example with this set I saw in my logs:

    "DEBUG""DEBUG""DEBUG""DEBUG"

Instead just rely on the default formatter, which will:

> ... log the level, date, source and line number of the
caller, followed by the arguments.

0 files changed, 0 insertions, 0 deletions