Update squizlabs/php_codesniffer to phpcsstandards/php_codesniffer

[andybroomfield]

See annoucement here squizlabs/PHP_CodeSniffer#3932
Looks like we need to change this in require dev in composer.json, and communicate that to those who took this repo so they get the change.

$ composer why squizlabs/php_codesniffer
localgovdrupal/localgov-project                3.x-dev  requires (for development) squizlabs/php_codesniffer (^3.6)                   
chi-teck/drupal-code-generator                 3.3.0    conflicts                  squizlabs/php_codesniffer (<3.6)                   
dealerdirect/phpcodesniffer-composer-installer v1.0.0   requires                   squizlabs/php_codesniffer (^2.0 || ^3.1.0 || ^4.0) 
drupal/coder                                   8.3.22   requires                   squizlabs/php_codesniffer (^3.7.1)                 
sirbrillig/phpcs-variable-analysis             v2.11.17 requires                   squizlabs/php_codesniffer (^3.5.6)                 
slevomat/coding-standard                       8.14.1   requires                   squizlabs/php_codesniffer (^3.7.1)