Bump fastjson from 1.2.73 to 1.2.83 in /backend

Bumps [fastjson](https://github.com/alibaba/fastjson) from 1.2.73 to 1.2.83.
- [Release notes](https://github.com/alibaba/fastjson/releases)
- [Commits](https://github.com/alibaba/fastjson/compare/1.2.73...1.2.83)

---
updated-dependencies:
- dependency-name: com.alibaba:fastjson
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/backend/pom.xml b/backend/pom.xml
index 45d3bea..c61b1ad 100644
--- a/backend/pom.xml
+++ b/backend/pom.xml
@@ -92,7 +92,7 @@
     <dependency>
       <groupId>com.alibaba</groupId>
       <artifactId>fastjson</artifactId>
-      <version>1.2.73</version>
+      <version>1.2.83</version>
     </dependency>
 
     <dependency>