[PATCH 2 of 2] Fixed article in "if_modified_since before"

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1672783715 -10800
#      Wed Jan 04 01:08:35 2023 +0300
# Node ID 547303412ab9bf1b22820b459143bd48d051f92f
# Parent  52ea1f45b324b404941a9b31b2861612cf090fcd
Fixed article in "if_modified_since before".

diff --git a/xml/en/docs/http/ngx_http_core_module.xml b/xml/en/docs/http/ngx_http_core_module.xml
--- a/xml/en/docs/http/ngx_http_core_module.xml
+++ b/xml/en/docs/http/ngx_http_core_module.xml
@@ -802,7 +802,7 @@ exact match;
 
 <tag-name><literal>before</literal></tag-name>
 <tag-desc>
-modification time of a response is
+modification time of the response is
 less than or equal to the time in the <header>If-Modified-Since</header>
 request header field.
 </tag-desc>