Documentation update to MessageSizeEstimator (#9034)

Motivation:

Did not understand the context of "ca".

Modification:

Clarified "CA" to "approximately".

Result:

Fixes #9031

transport/src/main/java/io/netty/channel/MessageSizeEstimator.java

@@ -16,8 +16,8 @@
 package io.netty.channel;
 
 /**
- * Responsible to estimate size of a message. The size represent how much memory the message will ca. reserve in
- * memory.
+ * Responsible to estimate the size of a message. The size represents approximately how much memory the message will
+ * reserve in memory.
  */
 public interface MessageSizeEstimator {