Bump dropwizard-bom from 2.0.13 to 2.0.15

Bumps [dropwizard-bom](https://github.com/dropwizard/dropwizard) from 2.0.13 to 2.0.15.
- [Release notes](https://github.com/dropwizard/dropwizard/releases)
- [Changelog](https://github.com/dropwizard/dropwizard/blob/master/RELEASES.md)
- [Commits](dropwizard/dropwizard@v2.0.13...v2.0.15)

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

Author: dependabot-preview[bot]

pom.xml

@@ -10,7 +10,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <mainClass>uk.gov.pay.ledger.app.LedgerApp</mainClass>
 
-        <dropwizard.version>2.0.13</dropwizard.version>
+        <dropwizard.version>2.0.15</dropwizard.version>
         <jackson.version>2.11.3</jackson.version>
         <testcontainers.version>1.14.3</testcontainers.version>
         <postgresql.version>42.2.17</postgresql.version>