DOC: configuration: fix alphabetical ordering for tune.pool-{high,low}-fd-ratio

In addition they were in the wrong alphabetical order in the doc. They
were added in 2.0 by commit 88698d966 ("MEDIUM: connections: Add a way
to control the number of idling connections.") so this must be backported
to 2.0.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index de7384b..dd166e7 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2063,12 +2063,6 @@
   performed. This has an impact on the kernel's memory footprint, so this must
   not be changed if impacts are not understood.
 
-tune.pool-low-fd-ratio <number>
-  This setting sets the max number of file descriptors (in percentage) used by
-  haproxy globally against the maximum number of file descriptors haproxy can
-  use before we stop putting connection into the idle pool for reuse. The
-  default is 20.
-
 tune.pool-high-fd-ratio <number>
   This setting sets the max number of file descriptors (in percentage) used by
   haproxy globally against the maximum number of file descriptors haproxy can
@@ -2078,6 +2072,12 @@
   keep an idle connection behind, anything beyond this probably doesn't make
   much sense in the general case when targeting connection reuse).
 
+tune.pool-low-fd-ratio <number>
+  This setting sets the max number of file descriptors (in percentage) used by
+  haproxy globally against the maximum number of file descriptors haproxy can
+  use before we stop putting connection into the idle pool for reuse. The
+  default is 20.
+
 tune.rcvbuf.client <number>
 tune.rcvbuf.server <number>
   Forces the kernel socket receive buffer size on the client or the server side