cups_proxy/proxy_manager.h: Increase rate limit to 40

tast.printer.ProxyPinPrintLexmark.no_pin appears to be failing due to
throttling. Increase the rate limit to prevent this.

Bug: 1157699
Change-Id: I51b4268551bdcee5003be84c161e2a8ff9894df4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586757Reviewed-by: Sean Kau <skau@chromium.org>
Commit-Queue: Sean Kau <skau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836207}

chrome/services/cups_proxy/proxy_manager.h

@@ -32,7 +32,7 @@ class SocketManager;
 class ProxyManager : public mojom::CupsProxier {
  public:
   // Request rate limit per second.
-  static constexpr int kRateLimit = 20;
+  static constexpr int kRateLimit = 40;
 
   // Factory function.
   static std::unique_ptr<ProxyManager> Create(