[misc] drop unused dependency pngcrush

services/filestore/package-lock.json

@@ -2556,11 +2556,6 @@
         "assert-plus": "^1.0.0"
       }
     },
-    "gettemporaryfilepath": {
-      "version": "0.0.1",
-      "resolved": "https://registry.npmjs.org/gettemporaryfilepath/-/gettemporaryfilepath-0.0.1.tgz",
-      "integrity": "sha512-7avwQWP8MP42u7mtc+KjCRuUE3nafRJPuGaZaySD9NN1KEbfVTfSAywP4KOkK8gaxhdOxx11ZTWH28DwjAF70Q=="
-    },
     "glob": {
       "version": "7.1.6",
       "resolved": "https://registry.npmjs.org/glob/-/glob-7.1.6.tgz",
@@ -3909,14 +3904,6 @@
         "find-up": "^2.1.0"
       }
     },
-    "pngcrush": {
-      "version": "0.0.3",
-      "resolved": "https://registry.npmjs.org/pngcrush/-/pngcrush-0.0.3.tgz",
-      "integrity": "sha512-RVaPWGv0PUUzGeSQJHH78rw2ks8NxKbFn8uENFM+/3bfsUs39MaFDG+eul5902gH97zZLQ0zd0h2yb0YBaMKDw==",
-      "requires": {
-        "gettemporaryfilepath": "=0.0.1"
-      }
-    },
     "prelude-ls": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.1.2.tgz",

services/filestore/package.json

@@ -30,7 +30,6 @@
     "logger-sharelatex": "^1.7.0",
     "metrics-sharelatex": "^2.2.0",
     "node-uuid": "~1.4.1",
-    "pngcrush": "0.0.3",
     "range-parser": "^1.0.2",
     "request": "^2.88.0",
     "request-promise-native": "^1.0.8",