chore(deps): bump excon from 1.3.0 to 1.5.0 in /images/fluentd/outputs

Bumps [excon](https://github.com/excon/excon) from 1.3.0 to 1.5.0.
- [Changelog](https://github.com/excon/excon/blob/master/changelog.txt)
- [Commits](excon/excon@v1.3.0...v1.5.0)

---
updated-dependencies:
- dependency-name: excon
  dependency-version: 1.5.0
  dependency-type: indirect
...

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

Author: dependabot[bot]

images/fluentd/outputs/Gemfile.lock

@@ -97,7 +97,7 @@ GEM
     ethon (0.18.0)
       ffi (>= 1.15.0)
       logger
-    excon (1.3.0)
+    excon (1.5.0)
       logger
     faraday (2.14.3)
       faraday-net_http (>= 2.0, < 3.5)