<C-K> keymap conflict in handlers and keymap fix

[mssalkhalifah]

There was a conflict in handler's keymap:

vim.api.nvim_buf_set_keymap(bufnr, "n", "<C-K>", "<cmd>lua vim.lsp.buf.signature_help()<CR>", opts)

And: keymap("n", "<C-k>", "<C-w>k", opts)

And changed it to Lunarvim's keymap: <gs>