Clarify error message in Runnable Request (#3393)

* Clarify error message in Runnable Request for connection acquisition timeouts

Replacing "pool lease timeout" with "connection acquisition timeout"

* Update error message in Runnable Request

Changing "slowing" to "slow"

Author: davidh44

http-clients/netty-nio-client/src/main/java/software/amazon/awssdk/http/nio/netty/internal/utils/NettyUtils.java

@@ -115,7 +115,8 @@ private static String getMessageForTooManyAcquireOperationsError() {
         return "Maximum pending connection acquisitions exceeded. The request rate is too high for the client to keep up.\n"
 
                + "Consider taking any of the following actions to mitigate the issue: increase max connections, "
-               + "increase max pending acquire count, decrease pool lease timeout, or slowing the request rate.\n"
+               + "increase max pending acquire count, decrease connection acquisition timeout, or "
+               + "slow the request rate.\n"
 
                + "Increasing the max connections can increase client throughput (unless the network interface is already "
                + "fully utilized), but can eventually start to hit operation system limitations on the number of file "