Bump beetl from 3.1.5.RELEASE to 3.1.6.RELEASE

Bumps [beetl](https://github.com/javamonkey/beetl2.0) from 3.1.5.RELEASE to 3.1.6.RELEASE.
- [Release notes](https://github.com/javamonkey/beetl2.0/releases)
- [Commits](https://github.com/javamonkey/beetl2.0/commits)

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

build.gradle

@@ -75,7 +75,7 @@ ext {
         //code generator
         "velocity"                   : "org.apache.velocity:velocity-engine-core:2.2",
         "freemarker"                 : "org.freemarker:freemarker:2.3.30",
-        "beetl"                      : "com.ibeetl:beetl:3.1.5.RELEASE",
+        "beetl"                      : "com.ibeetl:beetl:3.1.6.RELEASE",
         "swagger-annotations"        : "io.swagger:swagger-annotations:1.6.1",
         //cache
         "mybatis-ehcache"            : "org.mybatis.caches:mybatis-ehcache:1.2.1",