api center fix case (#25534)

Author: XiaofeiCao

specification/apicenter/resource-manager/readme.java.md

@@ -0,0 +1,7 @@
+## Java
+
+These settings apply only when `--java` is specified on the command line.
+
+```yaml $(java)
+service-name: ApiCenter
+```

specification/apicenter/resource-manager/readme.md

@@ -77,3 +77,7 @@ See configuration in [readme.typescript.md](./readme.typescript.md)
 ## CSharp
 
 See configuration in [readme.csharp.md](./readme.csharp.md)
+
+## Java
+
+See configuration in [readme.java.md](./readme.java.md)