Avoid ambiguous "that"

Author: Justin Pryzby

doc/src/sgml/config.sgml

@@ -3945,7 +3945,7 @@ include_dir 'conf.d'
         limit the amount of dirty data in the kernel's page cache, reducing
         the likelihood of stalls when an <function>fsync</function> is issued at the end of the
         checkpoint, or when the OS writes data back in larger batches in the
-        background.  Often that will result in greatly reduced transaction
+        background.  This feature will often result in greatly reduced transaction
         latency, but there also are some cases, especially with workloads
         that are bigger than <xref linkend="guc-shared-buffers"/>, but smaller
         than the OS's page cache, where performance might degrade.  This