Bump libphonenumber from 8.12.14 to 8.12.15

Bumps [libphonenumber](https://github.com/google/libphonenumber) from 8.12.14 to 8.12.15.
- [Release notes](https://github.com/google/libphonenumber/releases)
- [Changelog](https://github.com/google/libphonenumber/blob/master/making-metadata-changes.md)
- [Commits](google/libphonenumber@v8.12.14...v8.12.15)

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

pom.xml

@@ -186,7 +186,7 @@
         <dependency>
             <groupId>com.googlecode.libphonenumber</groupId>
             <artifactId>libphonenumber</artifactId>
-            <version>8.12.14</version>
+            <version>8.12.15</version>
         </dependency>
         <dependency>
             <groupId>uk.gov.pay</groupId>