docs: adjust descriptions

Co-authored-by: Zaiming (Stone) Shi <zmstone@gmail.com>

apps/emqx/i18n/emqx_schema_i18n.conf

@@ -1844,11 +1844,11 @@ Maximum time duration allowed for the handshake to complete
 server_ssl_opts_schema_gc_after_handshake {
     desc {
         en: """
-Performance tuning.  If enabled, will immediately perform a GC after
-the TLS/SSL handshake is established.
+Memory usage tuning. If enabled, will immediately perform a garbage collection after
+the TLS/SSL handshake.
 """
         zh: """
-性能调整。 如果启用，将在TLS/SSL握手建立后立即执行GC。
+内存使用调优。如果启用，将在TLS/SSL握手完成后立即执行垃圾回收。
 TLS/SSL握手建立后立即进行GC。
 """
     }