Bump mailer from 1.6 to 448.v5b_97805e3767

Bumps [mailer](https://github.com/jenkinsci/mailer-plugin) from 1.6 to 448.v5b_97805e3767.
- [Release notes](https://github.com/jenkinsci/mailer-plugin/releases)
- [Commits](https://github.com/jenkinsci/mailer-plugin/commits)

---
updated-dependencies:
- dependency-name: org.jenkins-ci.plugins:mailer
  dependency-type: direct:production
...

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

pom.xml

@@ -70,7 +70,7 @@
     <dependency>
       <groupId>org.jenkins-ci.plugins</groupId>
       <artifactId>mailer</artifactId>
-      <version>1.6</version>
+      <version>448.v5b_97805e3767</version>
     </dependency>
   </dependencies>