chore: bump version of http-signature to ^1.3.6 (#1889)

Co-authored-by: nickbarrett <nick.barrett@engineering.digital.dwp.gov.uk>

Author: nbarrett

package.json

@@ -99,7 +99,7 @@
     "ewma": "^2.0.1",
     "find-my-way": "^2.0.1",
     "formidable": "^1.2.1",
-    "http-signature": "^1.2.0",
+    "http-signature": "^1.3.6",
     "lodash": "^4.17.11",
     "lru-cache": "^5.1.1",
     "mime": "^2.4.3",