Majority of the messages are in the format ":attribute must
{conditions_to_be_met}", however a few inconsistently use "may" instead
of "must".
This PR fixes that and has them all use "must" instead.
To highlight the inconsistency:
```php
// "may"
'max' => [
'numeric' => 'The :attribute may not be greater than :max.',
'file' => 'The :attribute may not be greater than :max kilobytes.',
'string' => 'The :attribute may not be greater than :max characters.',
'array' => 'The :attribute may not have more than :max items.',
],
// "must"
'min' => [
'numeric' => 'The :attribute must be at least :min.',
'file' => 'The :attribute must be at least :min kilobytes.',
'string' => 'The :attribute must be at least :min characters.',
'array' => 'The :attribute must have at least :min items.',
],
```
c988335502