Fix handling false which is returned by hint_inline function

[Sheile]

Overview

The lsp_signature displays hint in the same line also if specify function which will return false to disable inline hint.

Cause

_LSP_SIG_CFG.hint_inline is function and it is evaluated as truthy value.

Options

opts = {
  hint_inline = function() return false end,  -- default
  hint_prefix = {
    above = "↙ ",
    current = "←  ",
    below = "↖ "
  },
}

Expected behavior ( or patched version behavior)

Actual behavior

[ray-x]

Thanks, I will update doc as well