Update downloadGJMessage20.md

Fix description

Author: WOSHIZHAZHA120

docs/endpoints/downloadGJMessage20.md

@@ -1,6 +1,6 @@
 # downloadGJMessage20.php
 
-Blocks a user.
+Download a message.
 
 ## Parameters
 
@@ -53,4 +53,4 @@ print(req.text)
 6:DevExit:3:3935672:2:173831:1:54109536:4:WW91J3JlIGR1bWIgbG9s:8:1:9:0:5:TWhtIHllcCB5b3UncmUgcCBkdW1iIGxtYW8=:7:19 minutes
 ```
 
-<!-- tabs:end -->
+<!-- tabs:end -->