GEODE-10089: Bump version to 1.15.1

As part of the Geode Release Process, the geode-benchmarks build number
must be rolled forward as work begins on the next release
diff --git a/gradle.properties b/gradle.properties
index 68c1dcc..f09c6f3 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 # The versionNumber follows semantic versioning conventions.
-versionNumber = 1.15.0
+versionNumber = 1.15.1
 
 # The releaseQualifier uses the following conventions:
 #   .M?       - milestone release