docs: Remove slash from test4 endpoint (gnolang#2603)

The trailing slash at the end of the test4 endpoint seems redundant. I
suggest removing it for consistency


https://github.com/gnolang/gno/blob/master/docs/reference/network-config.md?plain=1#L1-L19

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- [ ] Added new tests, or not needed, or not feasible
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docs/reference/network-config.md

@@ -7,7 +7,7 @@ id: network-config
 | Network | RPC Endpoint | Chain ID | 
 |-------------|-----------------------------------|---------------|
 | Portal Loop | https://rpc.gno.land:443 | `portal-loop` |
-| Test4 | https://rpc.test4.gno.land:443/ | `test4` |
+| Test4 | https://rpc.test4.gno.land:443  | `test4` |
 | Test3 | https://rpc.test3.gno.land:443 | `test3` |
 | Staging | http://rpc.staging.gno.land:36657 | `staging` |