fix: upgrade dockerfile-ast from 0.6.1 to 0.7.1 (#694)

Snyk has created this PR to upgrade dockerfile-ast from 0.6.1 to 0.7.1.

See this package in npm:
dockerfile-ast

See this project in Snyk:
https://app.snyk.io/org/snyk-apprisk-essentials-closed-beta-demo-group/project/84136c30-73f1-432e-90ed-17f0749249d9?utm_source=github&utm_medium=referral&page=upgrade-pr

Co-authored-by: snyk-bot <snyk-bot@snyk.io>

Author: denis-snyk

package-lock.json

@@ -38,7 +38,7 @@
     "chalk": "^2.4.2",
     "debug": "^4.4.1",
     "docker-modem": "^3.0.8",
-    "dockerfile-ast": "^0.6.1",
+    "dockerfile-ast": "^0.7.1",
     "elfy": "^1.0.0",
     "event-loop-spinner": "^2.3.2",
     "gunzip-maybe": "^1.4.2",