Bump acorn from 6.1.1 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.1.1 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/6.1.1...6.4.1)

Signed-off-by: dependabot[bot] <support@github.com>

package-lock.json

@@ -1100,9 +1100,9 @@
             }
         },
         "acorn": {
-            "version": "6.1.1",
-            "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.1.1.tgz",
-            "integrity": "sha512-jPTiwtOxaHNaAPg/dmrJ/beuzLRnXtB0kQPQ8JpotKJgTB6rX6c8mlf315941pyjBSaPg8NHXS9fhP4u17DpGA==",
+            "version": "6.4.1",
+            "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.4.1.tgz",
+            "integrity": "sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==",
             "dev": true
         },
         "acorn-dynamic-import": {
@@ -3822,7 +3822,8 @@
                 "ansi-regex": {
                     "version": "2.1.1",
                     "bundled": true,
-                    "dev": true
+                    "dev": true,
+                    "optional": true
                 },
                 "aproba": {
                     "version": "1.2.0",
@@ -4031,12 +4032,14 @@
                 "minimist": {
                     "version": "0.0.8",
                     "bundled": true,
-                    "dev": true
+                    "dev": true,
+                    "optional": true
                 },
                 "minipass": {
                     "version": "2.3.5",
                     "bundled": true,
                     "dev": true,
+                    "optional": true,
                     "requires": {
                         "safe-buffer": "^5.1.2",
                         "yallist": "^3.0.0"
@@ -4055,6 +4058,7 @@
                     "version": "0.5.1",
                     "bundled": true,
                     "dev": true,
+                    "optional": true,
                     "requires": {
                         "minimist": "0.0.8"
                     }
@@ -4234,7 +4238,8 @@
                 "safe-buffer": {
                     "version": "5.1.2",
                     "bundled": true,
-                    "dev": true
+                    "dev": true,
+                    "optional": true
                 },
                 "safer-buffer": {
                     "version": "2.1.2",
@@ -4290,6 +4295,7 @@
                     "version": "3.0.1",
                     "bundled": true,
                     "dev": true,
+                    "optional": true,
                     "requires": {
                         "ansi-regex": "^2.0.0"
                     }
@@ -4333,12 +4339,14 @@
                 "wrappy": {
                     "version": "1.0.2",
                     "bundled": true,
-                    "dev": true
+                    "dev": true,
+                    "optional": true
                 },
                 "yallist": {
                     "version": "3.0.3",
                     "bundled": true,
-                    "dev": true
+                    "dev": true,
+                    "optional": true
                 }
             }
         },
@@ -7219,7 +7227,7 @@
         },
         "readable-stream": {
             "version": "2.3.6",
-            "resolved": "http://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
+            "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.6.tgz",
             "integrity": "sha512-tQtKA9WIAhBF3+VLAseyMqZeBjW0AHJoxOtYqSUZNJxauErmLbVm2FW1y+J/YA9dUrAC39ITejlZWhVIwawkKw==",
             "dev": true,
             "requires": {