tests: quote test break compatibility with older Perl versions

[dveeden]

Type of arg 1 to each must be hash (not private array) at t/17quote.t line 28, near "@sqlmodes) "
Execution of t/17quote.t aborted due to compilation errors.
t/17quote.t ............................. 
Dubious, test returned 255 (wstat 65280, 0xff00)

Source: https://www.cpantesters.org/cpan/report/9af6460e-8125-11ef-9009-601eda8747de

This is with perl 5.10.1

This line is the problem:

DBD-mysql/t/17quote.t

Line 28 in 5a669fb

while (my ($i, $sqlmode) = each @sqlmodes) {

See also https://perldoc.perl.org/functions/each