build(deps): [security] bump sshpk from 1.13.1 to 1.15.2 (#499)

Bumps [sshpk](https://github.com/joyent/node-sshpk) from 1.13.1 to 1.15.2. **This update includes security fixes.**
- [Release notes](https://github.com/joyent/node-sshpk/releases)
- [Commits](https://github.com/joyent/node-sshpk/compare/v1.13.1...v1.15.2)
Signed-off-by: dependabot[bot] <support@dependabot.com>

package-lock.json

@@ -2073,7 +2073,6 @@
       "resolved": "https://registry.npmjs.org/bcrypt-pbkdf/-/bcrypt-pbkdf-1.0.1.tgz",
       "integrity": "sha1-Y7xdy2EzG5K8Bf1SiVPDNGKgb40=",
       "dev": true,
-      "optional": true,
       "requires": {
         "tweetnacl": "^0.14.3"
       }
@@ -3716,7 +3715,6 @@
       "resolved": "https://registry.npmjs.org/ecc-jsbn/-/ecc-jsbn-0.1.1.tgz",
       "integrity": "sha1-D8c6ntXw1Tw4GTOYUj735UN3dQU=",
       "dev": true,
-      "optional": true,
       "requires": {
         "jsbn": "~0.1.0"
       }
@@ -7791,8 +7789,7 @@
       "version": "0.1.1",
       "resolved": "https://registry.npmjs.org/jsbn/-/jsbn-0.1.1.tgz",
       "integrity": "sha1-peZUwuWi3rXyAdls77yoDA7y9RM=",
-      "dev": true,
-      "optional": true
+      "dev": true
     },
     "jscodeshift": {
       "version": "0.5.0",
@@ -10885,6 +10882,12 @@
         "ret": "~0.1.10"
       }
     },
+    "safer-buffer": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/safer-buffer/-/safer-buffer-2.1.2.tgz",
+      "integrity": "sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==",
+      "dev": true
+    },
     "sane": {
       "version": "2.5.2",
       "resolved": "https://registry.npmjs.org/sane/-/sane-2.5.2.tgz",
@@ -12317,9 +12320,9 @@
       "dev": true
     },
     "sshpk": {
-      "version": "1.13.1",
-      "resolved": "https://registry.npmjs.org/sshpk/-/sshpk-1.13.1.tgz",
-      "integrity": "sha1-US322mKHFEMW3EwY/hzx2UBzm+M=",
+      "version": "1.15.2",
+      "resolved": "https://registry.npmjs.org/sshpk/-/sshpk-1.15.2.tgz",
+      "integrity": "sha512-Ra/OXQtuh0/enyl4ETZAfTaeksa6BXks5ZcjpSUNrjBr0DvrJKX+1fsKDPpT9TBXgHAFsa4510aNVgI8g/+SzA==",
       "dev": true,
       "requires": {
         "asn1": "~0.2.3",
@@ -12329,6 +12332,7 @@
         "ecc-jsbn": "~0.1.1",
         "getpass": "^0.1.1",
         "jsbn": "~0.1.0",
+        "safer-buffer": "^2.0.2",
         "tweetnacl": "~0.14.0"
       }
     },
@@ -13371,8 +13375,7 @@
       "version": "0.14.5",
       "resolved": "https://registry.npmjs.org/tweetnacl/-/tweetnacl-0.14.5.tgz",
       "integrity": "sha1-WuaBd/GS1EViadEIr6k/+HQ/T2Q=",
-      "dev": true,
-      "optional": true
+      "dev": true
     },
     "type-check": {
       "version": "0.3.2",