Update @kredits/contracts to 7.5.1

7.5.1 fixes IPFS cat() decoding for ipfs-http-client 56 (Uint8Array chunks),
which broke contributor profile reads and stopped hubot-kredits from
proposing kredits. This lockfile is what nodejs-5 installs, so it is the
actual deploy gate.

package-lock.json

@@ -805,9 +805,9 @@
       "license": "MIT"
     },
     "node_modules/@kredits/contracts": {
-      "version": "7.5.0",
-      "resolved": "https://registry.npmjs.org/@kredits/contracts/-/contracts-7.5.0.tgz",
-      "integrity": "sha512-4Jw6lXn9DfZiTnMtWHwGLS5zhxEJZ2ANfAgcr7tZxqRl7Y0ijpoWvPCA+LkSGqRgKspyiw9+7vSVTtyvAyQbPQ==",
+      "version": "7.5.1",
+      "resolved": "https://registry.npmjs.org/@kredits/contracts/-/contracts-7.5.1.tgz",
+      "integrity": "sha512-mZlU+b9RN3wUZaxVM8xa6gQ1FkpyfyG5SmGjTpC2cXcaOVMOJRx1fgMLyVhyXCQFWhDPWuZ3HPb/a9czUYf+2A==",
       "license": "MIT",
       "dependencies": {
         "@kosmos/schemas": "^3.2.0",