[Security] Bump sshpk from 1.13.1 to 1.16.0 in /backend

[dependabot-preview]

Bumps sshpk from 1.13.1 to 1.16.0. This update includes security fixes.

Vulnerabilities fixed

Sourced from The npm Advisory Database.

Regular Expression Denial of Service
Versions of sshpk before 1.13.2 or 1.14.1 are vulnerable to regular expression denial of service when parsing crafted invalid public keys.

Affected versions: <1.13.2; >=1.14.0 <1.14.1

Sourced from The GitHub Security Advisory Database.

Moderate severity vulnerability that affects sshpk
The sshpk NPM package is vulnerable to ReDoS when parsing crafted invalid public keys.

Affected versions: < 1.13.2

Sourced from The Node Security Working Group.

Denial of Service
sshpk is vulnerable to ReDoS when parsing crafted invalid public keys

Affected versions: <=1.13.1

Release notes

Sourced from sshpk's releases.

v1.16.0

• Add support for SPKI fingerprints, PuTTY PPK format (public-key only for now), PKCS#8 PBKDF2 encrypted private keys
• Fix for #48

v1.15.2

• New API for accessing x509 extensions in certificates
• Fixes for #52, #50

v1.14.1

• Remove all remaining usage of jodid25519 (abandoned dep)
• Add support for DNSSEC key format
• Add support for Ed25519 keys in PEM format (according to draft-curdle-pkix)
• Fixes for X.509 encoding issues (asn.1 NULLs in RSA certs, cert string type mangling)
• Performance issues parsing long SSH public keys

Commits

• 574ff21 support for PKCS8 encrypted private keys TritonDataCenter/node-sshpk#18 support for PKCS8 encrypted private keys
• f647cf2 Add support for PuTTY PPK format TritonDataCenter/node-sshpk#27 Add support for PuTTY PPK format
• 44aec4a want support for SPKI fingerprint format TritonDataCenter/node-sshpk#59 want support for SPKI fingerprint format
• 385ff11 wish: add support for x509 certificates in text form TritonDataCenter/node-sshpk#48 wish: add support for x509 certificates in text form
• c7a6c68 des-ede3-cbc encrypted keys broken TritonDataCenter/node-sshpk#58 des-ede3-cbc encrypted keys broken
• 2ab4f2a md5 fingerprints not quite right TritonDataCenter/node-sshpk#56 md5 fingerprints not quite right
• 026ef47 stop using optional deps to fix webpack TritonDataCenter/node-sshpk#53 stop using optional deps to fix webpack
• 53e23fe Support PKCS#5 AES-256-CBC encrypted private keys TritonDataCenter/node-sshpk#50 Support PKCS#5 AES-256-CBC encrypted private keys
• 6b68d49 want API for accessing x509 extensions TritonDataCenter/node-sshpk#54 want API for accessing x509 extensions
• 1088992 Buffer no longer performs length check for hex strings in node v8.x  TritonDataCenter/node-sshpk#52 Buffer no longer performs length check for hex strings i...
• Additional commits viewable in compare view

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Superseded by #357.