Merge pull request #11444 from taosdata/docs/dingbo/TD-14075

docs: hightlight R language

docs-cn/04-connect/_connect_r.mdx

-```R
+```r
 > library("DBI")
 > library("rJava")
 > library("RJDBC")

docs-cn/04-connect/index.mdx

@@ -130,7 +130,7 @@ dotnet add package TDengine.Connector
 <TabItem label="R" value="r">
 
 首先系统上要有 TDeninge 客户端驱动，安装目录下有`connector/jdbc/taos-jdbcdriver-xxx-dist.jar`。然后需要安装 R 的依赖包`RJDBC`：
-```R
+```r
 install.packages("RJDBC")
 ```