Bump bootstrap from 3.3.7 to 3.4.1 in /src (#1021)

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 3.3.7 to 3.4.1.
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](https://github.com/twbs/bootstrap/compare/v3.3.7...v3.4.1)

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

src/package-lock.json

@@ -130,9 +130,9 @@
       }
     },
     "bootstrap": {
-      "version": "3.3.7",
-      "resolved": "https://registry.npmjs.org/bootstrap/-/bootstrap-3.3.7.tgz",
-      "integrity": "sha1-WjiTlFSfIzMIdaOxUGVldPip63E="
+      "version": "3.4.1",
+      "resolved": "https://registry.npmjs.org/bootstrap/-/bootstrap-3.4.1.tgz",
+      "integrity": "sha512-yN5oZVmRCwe5aKwzRj6736nSmKDX7pLYwsXiCj/EYmo16hODaBiT4En5btW/jhBF/seV+XMx3aYwukYC3A49DA=="
     },
     "brace-expansion": {
       "version": "1.1.11",