Bump mailgun-ruby from 1.3.10 to 1.4.0 (#179)

Bumps [mailgun-ruby](https://github.com/mailgun/mailgun-ruby) from 1.3.10 to 1.4.0.
- [Release notes](https://github.com/mailgun/mailgun-ruby/releases)
- [Changelog](https://github.com/mailgun/mailgun-ruby/blob/master/CHANGELOG.md)
- [Commits](mailgun/mailgun-ruby@v1.3.10...v1.4.0)

---
updated-dependencies:
- dependency-name: mailgun-ruby
  dependency-version: 1.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -174,7 +174,7 @@ GEM
     factory_bot_rails (6.5.1)
       factory_bot (~> 6.5)
       railties (>= 6.1.0)
-    faraday (2.13.4)
+    faraday (2.14.0)
       faraday-net_http (>= 2.0, < 3.5)
       json
       logger
@@ -249,7 +249,7 @@ GEM
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
-    json (2.13.2)
+    json (2.15.1)
     jwt (2.10.2)
       base64
     language_server-protocol (3.17.0.5)
@@ -263,7 +263,7 @@ GEM
       net-imap
       net-pop
       net-smtp
-    mailgun-ruby (1.3.10)
+    mailgun-ruby (1.4.0)
       faraday (~> 2.1)
       faraday-multipart (~> 1.1.0)
       mini_mime
@@ -537,7 +537,7 @@ GEM
     unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
-    uri (1.0.3)
+    uri (1.0.4)
     useragent (0.16.11)
     valid_email2 (7.0.13)
       activemodel (>= 6.0)