Revisit usage of deprecated `reflect.StringHeader`

[M4tteoP]

reflect.StringHeader has been deprecated since Go 1.22. Context of our usage: #553

coraza/internal/corazawaf/rule.go

Line 402 in be8c6af

argKeyPtr := (*reflect.StringHeader)(unsafe.Pointer(&argKey)).Data // nolint:staticcheck

See also #1145 (comment) for a possible alternative (to be further explored and tested).