Bump eventsource from 1.1.0 to 1.1.1 in /examples/vanilla (#1466)

Bumps [eventsource](https://github.com/EventSource/eventsource) from 1.1.0 to 1.1.1.
- [Release notes](https://github.com/EventSource/eventsource/releases)
- [Changelog](https://github.com/EventSource/eventsource/blob/master/HISTORY.md)
- [Commits](EventSource/eventsource@v1.1.0...v1.1.1)

---
updated-dependencies:
- dependency-name: eventsource
  dependency-type: indirect
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

examples/vanilla/yarn.lock

@@ -926,9 +926,9 @@ events@^3.2.0:
   integrity sha512-mQw+2fkQbALzQ7V0MY0IqdnXNOeTtP4r0lN9z7AAawCXgqea7bDii20AYrIBrFd/Hx0M2Ocz6S111CaFkUcb0Q==
 
 eventsource@^1.0.7:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/eventsource/-/eventsource-1.1.0.tgz#00e8ca7c92109e94b0ddf32dac677d841028cfaf"
-  integrity sha512-VSJjT5oCNrFvCS6igjzPAt5hBzQ2qPBFIbJ03zLI9SE0mxwZpMw6BfJrbFHm1a141AavMEB8JHmBhWAd66PfCg==
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/eventsource/-/eventsource-1.1.1.tgz#4544a35a57d7120fba4fa4c86cb4023b2c09df2f"
+  integrity sha512-qV5ZC0h7jYIAOhArFJgSfdyz6rALJyb270714o7ZtNnw2WSJ+eexhKtE0O8LYPRsHZHf2osHKZBxGPvm3kPkCA==
   dependencies:
     original "^1.0.0"