docs: refine a statement

docs-examples/go/connect/cgoexample/main.go

@@ -20,4 +20,4 @@ func main() {
 
 // use
 // var taosDSN = "root:taosdata@tcp(localhost:6030)/dbName"
-// if you want to connect to a default database.
+// if you want to connect a specified database named "dbName".

docs-examples/go/connect/restexample/main.go

@@ -18,6 +18,6 @@ func main() {
 	defer taos.Close()
 }
 
-// use 
+// use
 // var taosDSN = "root:taosdata@http(localhost:6041)/dbName"
-// if you want to connect to a default database.
+// if you want to connect a specified database named "dbName".

docs-examples/java/src/main/java/com/taos/example/JNIConnectExample.java

@@ -22,4 +22,4 @@ public class JNIConnectExample {
 
 // use
 // String jdbcUrl = "jdbc:TAOS://localhost:6030/dbName?user=root&password=taosdata";
-// if you want to connect to a default database.
+// if you want to connect a specified database named "dbName".
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