Fix incorrect escaping of hunspell command

[cniry]

Fix incorrect slashing of hunspell command params, which causes "Can't open affix or dictionary files for dictionary named "default"" on Alpine Docker container.

This example script

$source = new StringSource('Tiger, tigr, burning bright');
$speller = new Hunspell();
$issues = $speller->checkText($source, ['en_US']);

was calling this command:

'hunspell' '-i UTF-8' '-a' '-d en_US'

Which is not correctly parsed by hunspell on Alpine Docker container and throws error Failed to execute "'hunspell' '-i UTF-8' '-a' '-d en_US'": Can't open affix or dictionary files for dictionary named "default".

Executing this command inside docker containter results same error.

now it calls:

'hunspell' '-i' 'UTF-8' '-a' '-d' 'en_US'

which is successflully parsed by hunspel. Tested on Hunspell 1.7.0