Bump abortcontroller-polyfill from 1.2.7 to 1.2.9 in /frontend

Bumps [abortcontroller-polyfill](https://github.com/mo/abortcontroller-polyfill) from 1.2.7 to 1.2.9.
- [Release notes](https://github.com/mo/abortcontroller-polyfill/releases)
- [Commits](mo/abortcontroller-polyfill@v1.2.7...v1.2.9)

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

Author: dependabot-support

frontend/package.json

@@ -4,7 +4,7 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "abortcontroller-polyfill": "^1.2.7",
+    "abortcontroller-polyfill": "^1.2.9",
     "bootstrap": "3",
     "codemirror": "^5.44.0",
     "nanoid": "^2.0.1",

frontend/yarn.lock

@@ -61,10 +61,10 @@ abbrev@1, abbrev@~1.1.1:
   resolved "https://registry.yarnpkg.com/abbrev/-/abbrev-1.1.1.tgz#f8f2c887ad10bf67f634f005b6987fed3179aac8"
   integrity sha512-nne9/IiQ/hzIhY6pdDnbBtz7DjPTKrY00P/zvPSm5pOFkl6xuGrGnXn/VtTNNfNtAfZ9/1RtehkszU9qcTii0Q==
 
-abortcontroller-polyfill@^1.2.7:
-  version "1.2.7"
-  resolved "https://registry.yarnpkg.com/abortcontroller-polyfill/-/abortcontroller-polyfill-1.2.7.tgz#8098f26b4c78eda96cf1ec49a961bacfe4f3d5b8"
-  integrity sha512-lk2K42684+p4JTE281GmRCxV7HkDYYGBkQYb3rIgUhDTl3l5Nwr4VpO2E/UXISmhmF3X6TnvgZTAa5Sh2cnPQQ==
+abortcontroller-polyfill@^1.2.9:
+  version "1.2.9"
+  resolved "https://registry.yarnpkg.com/abortcontroller-polyfill/-/abortcontroller-polyfill-1.2.9.tgz#402311d2aac7e8e093ecb045726b45fdafd834fe"
+  integrity sha512-0goWhDrwoWtK6XCdFdzPtvHBmmQU91j3tULNL85MAnDuM7bNlzUDfmL5AZGL819L7pn9kra35HJGWG25UgRCBw==
 
 accepts@~1.3.4, accepts@~1.3.5:
   version "1.3.5"