Bump is-svg and postcss-svgo in /frontend

Removes [is-svg](https://github.com/sindresorhus/is-svg). It's no longer used after updating ancestor dependency [postcss-svgo](https://github.com/cssnano/cssnano). These dependencies need to be updated together.


Removes `is-svg`

Updates `postcss-svgo` from 4.0.2 to 4.0.3
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/4.0.2...4.0.3)

---
updated-dependencies:
- dependency-name: is-svg
  dependency-type: indirect
- dependency-name: postcss-svgo
  dependency-type: indirect
...

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

frontend/package-lock.json

@@ -7711,11 +7711,6 @@
       "resolved": "https://registry.npmjs.org/hsla-regex/-/hsla-regex-1.0.0.tgz",
       "integrity": "sha1-wc56MWjIxmFAM6S194d/OyJfnDg="
     },
-    "html-comment-regex": {
-      "version": "1.1.2",
-      "resolved": "https://registry.npmjs.org/html-comment-regex/-/html-comment-regex-1.1.2.tgz",
-      "integrity": "sha512-P+M65QY2JQ5Y0G9KKdlDpo0zK+/OHptU5AaBwUfAIDJZk1MYf32Frm84EcOytfJE0t5JvkAnKlmjsXDnWzCJmQ=="
-    },
     "html-encoding-sniffer": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/html-encoding-sniffer/-/html-encoding-sniffer-1.0.2.tgz",
@@ -8349,14 +8344,6 @@
       "resolved": "https://registry.npmjs.org/is-string/-/is-string-1.0.5.tgz",
       "integrity": "sha512-buY6VNRjhQMiF1qWDouloZlQbRhDPCebwxSjxMjxgemYT46YMd2NR0/H+fBhEfWX4A/w9TBJ+ol+okqJKFE6vQ=="
     },
-    "is-svg": {
-      "version": "3.0.0",
-      "resolved": "https://registry.npmjs.org/is-svg/-/is-svg-3.0.0.tgz",
-      "integrity": "sha512-gi4iHK53LR2ujhLVVj+37Ykh9GLqYHX6JOVXbLAucaG/Cqw9xwdFOjDM2qeifLs1sF1npXXFvDu0r5HNgCMrzQ==",
-      "requires": {
-        "html-comment-regex": "^1.1.0"
-      }
-    },
     "is-symbol": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/is-symbol/-/is-symbol-1.0.3.tgz",
@@ -11951,11 +11938,10 @@
       }
     },
     "postcss-svgo": {
-      "version": "4.0.2",
-      "resolved": "https://registry.npmjs.org/postcss-svgo/-/postcss-svgo-4.0.2.tgz",
-      "integrity": "sha512-C6wyjo3VwFm0QgBy+Fu7gCYOkCmgmClghO+pjcxvrcBKtiKt0uCF+hvbMO1fyv5BMImRK90SMb+dwUnfbGd+jw==",
+      "version": "4.0.3",
+      "resolved": "https://registry.npmjs.org/postcss-svgo/-/postcss-svgo-4.0.3.tgz",
+      "integrity": "sha512-NoRbrcMWTtUghzuKSoIm6XV+sJdvZ7GZSc3wdBN0W19FTtp2ko8NqLsgoh/m9CzNhU3KLPvQmjIwtaNFkaFTvw==",
       "requires": {
-        "is-svg": "^3.0.0",
         "postcss": "^7.0.0",
         "postcss-value-parser": "^3.0.0",
         "svgo": "^1.0.0"