Bump lodash from 4.17.15 to 4.17.21 in /packages/squiggle-lang

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.15 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.15...4.17.21)

---
updated-dependencies:
- dependency-name: lodash
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

packages/squiggle-lang/package.json

@@ -19,7 +19,7 @@
   "dependencies": {
     "@glennsl/bs-json": "^5.0.2",
     "jstat": "^1.9.5",
-    "lodash": "4.17.15",
+    "lodash": "4.17.21",
     "mathjs": "10.4.1",
     "pdfast": "^0.2.0",
     "rationale": "0.2.0",