dashboard: Update Spring Boot starter to 2.5.12

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Author: sczyh30

sentinel-dashboard/pom.xml

@@ -14,7 +14,7 @@
 
     <properties>
         <resource.delimiter>@</resource.delimiter>
-        <spring.boot.version>2.2.13.RELEASE</spring.boot.version>
+        <spring.boot.version>2.5.12</spring.boot.version>
         <curator.version>4.0.1</curator.version>
     </properties>