Validator: Remove early context cancellation. (#15369)

This is causing issues where submitting validator registrations and proposer settings were failing about 50% of the time in testing.

changelog/pvl-rm-ctx-rm.md

@@ -0,0 +1,3 @@
+### Fixed
+
+- Removed eager validator context cancellation that was causing validator builder registrations to fail occasionally.

validator/client/runner.go

@@ -123,7 +123,6 @@ func run(ctx context.Context, v iface.Validator) {
 				cancel()
 				continue
 			}
-			cancel()
 			// performRoles calls span.End()
 			rolesCtx, _ := context.WithDeadline(ctx, deadline)
 			performRoles(rolesCtx, allRoles, v, slot, &wg, span)