test(operators): improve "remaps gx" test after Nightly changes

Author: echasnovski

tests/test_operators.lua

@@ -140,7 +140,13 @@ end
 T['setup()']['remaps built-in `gx` mappings'] = function()
   if child.fn.has('nvim-0.10') == 0 then MiniTest.skip('Neovim<0.10 does not have built-in `gx` mappings') end
 
+  -- Mock functions used to compute and show URI at cursor
+  child.lua('vim.lsp.buf_request_sync = function() return {} end')
   child.lua('vim.ui.open = function() _G.n = (_G.n or 0) + 1 end')
+
+  set_lines({ 'https://nvim-mini.org' })
+  set_cursor(1, 0)
+
   local validate = function(keys, ref_n)
     type_keys(keys)
     eq(child.lua_get('_G.n'), ref_n)