Document that / is behave same as /** (#8791)

* Document that `/` is behave same as `/**`

See dotnet/runtime#80076 (comment)

* oops

Author: kant2002

xml/Microsoft.Extensions.FileSystemGlobbing/Matcher.xml

@@ -37,7 +37,7 @@
         </item>
         <item>
           <description>Arbitrary directory depth (<c>/**/</c>).
-            <list type="table"><listheader><term>Value</term><description>Description</description></listheader><item><term><c>**/*</c></term><description>All files in any subdirectory.</description></item><item><term><c>dir/**/*</c></term><description>All files in any subdirectory under 'dir/'.</description></item></list></description>
+            <list type="table"><listheader><term>Value</term><description>Description</description></listheader><item><term><c>**/*</c></term><description>All files in any subdirectory.</description></item><item><term><c>dir/**/*</c></term><description>All files in any subdirectory under 'dir/'.</description></item><item><term><c>dir/</c></term><description>All files in any subdirectory under 'dir/'.</description></item></list></description>
         </item>
         <item>
           <description>Relative paths.