fetchActions: Pull await backoffMachine.wait() out of catch block.

As Greg points out [1], this makes the most sense conceptually; it's
happening at the bottom of the loop, just before a new iteration
starts. The `return` in the `try` block is enough to ensure that
this wait won't interfere with a successful fetch.

[1]: zulip#4166 (comment)

Author: chrisbobbe

src/message/fetchActions.js

@@ -301,8 +301,8 @@ export async function tryFetch<T>(func: () => Promise<T>): Promise<T> {
             if (!isServerError(e)) {
               throw e;
             }
-            await backoffMachine.wait();
           }
+          await backoffMachine.wait();
         }
       })(),
       config.requestLongTimeoutMs,