Add missing access modifiers to SimpleRateLimitPolicy (#28389)

Author: sjvanrossum

sdks/java/io/google-ads/src/main/java/org/apache/beam/sdk/io/googleads/GoogleAdsV14.java

@@ -645,11 +645,11 @@ void onBeforeRequest(String developerToken, String customerId, Message request)
   public static class SimpleRateLimitPolicy implements RateLimitPolicy {
     private final RateLimiter rateLimiter;
 
-    SimpleRateLimitPolicy(double permitsPerSecond) {
+    public SimpleRateLimitPolicy(double permitsPerSecond) {
       rateLimiter = RateLimiter.create(permitsPerSecond);
     }
 
-    SimpleRateLimitPolicy(double permitsPerSecond, long warmupPeriod, TimeUnit unit) {
+    public SimpleRateLimitPolicy(double permitsPerSecond, long warmupPeriod, TimeUnit unit) {
       rateLimiter = RateLimiter.create(permitsPerSecond, warmupPeriod, unit);
     }