Update azure-dependencies-bom version to 2.1.0.M2. (#543)

Signed-off-by: Pan Li <panli@microsoft.com>

azure-spring-boot-bom/pom.xml

@@ -47,7 +47,7 @@
 
     <properties>
         <azure.spring.boot.version>${project.version}</azure.spring.boot.version>
-        <azure.dependencies.bom.version>2.1.0.M1</azure.dependencies.bom.version>
+        <azure.dependencies.bom.version>2.1.0.M2</azure.dependencies.bom.version>
     </properties>
 
     <dependencyManagement>