Custom keymaps on visual mode inserts extraneous character

When using a custom keymap in visual mode:

```lua
vim.keymap.set("v", "gaU", ":lua require('textcase').current_word('to_upper_case')<CR>")
```

it enters insert mode and leaves an additional `w` when done

```
fooBa*r <-- * is cursor in normal mode
```

1. `viw` to select the inner word
2. `gaU` to convert to uppercase

```
Fw*OOBAR <-- * is cursor in insert mode
```