Remove structured binding in x509_certificate.cc
Remove structured binding in x509_certificate.cc

This provides better compatibility with older versions of C++.

PiperOrigin-RevId: 279135599
Change-Id: Ic13fa661ec3fcac702b82e472e138dbef81c3915

google/asylo,google/asylo,google/asylo,google/asylo,google/asylo,google/asylo