Increase SSLProxyVerifyDepth to 8, since S3 has 4 certificates in chain
Seeing errors like this reverse proxying S3 urls:
[Wed Nov 03 18:58:31.887050 2021] [ssl:error] [pid 3228] [remote ip:443] AH02040: Certificate Verification: Certificate Chain too long (chain has 4 certificates, but maximum allowed are only 3)