fix(compute_ctl): remove stray variable in error message (#4823)

error is not needed because anyhow will have the cause chain reported
anyways.

related to test_neon_cli_basics being flaky, but doesn't actually fix
any flakyness, just the obvious stray `{e}`.

control_plane/src/endpoint.rs

@@ -564,9 +564,7 @@ impl Endpoint {
                 }
                 Err(e) => {
                     if attempt == MAX_ATTEMPTS {
-                        return Err(e).context(
-                            "timed out waiting to connect to compute_ctl HTTP; last error: {e}",
-                        );
+                        return Err(e).context("timed out waiting to connect to compute_ctl HTTP");
                     }
                 }
             }