doc: Fix an apparently no longer legal @itemize @asis

* basic.texi: @asis isn't legal with @itemize apparently, should be @w
  according to docs, but @w{} seems to be needed. Fixes doc build error.
diff --git a/doc/basic.texi b/doc/basic.texi
index 77fceee..b3b23ca 100644
--- a/doc/basic.texi
+++ b/doc/basic.texi
@@ -46,14 +46,14 @@
 
 Config files are generally found in:
 
-@itemize @asis
+@itemize @w{}
 @item @file{@value{INSTALL_PREFIX_ETC}/*.conf}
 @end itemize
 
 Each of the daemons has its own
 config file.  For example, zebra's default config file name is:
 
-@itemize @asis
+@itemize @w{}
 @item @file{@value{INSTALL_PREFIX_ETC}/zebra.conf}
 @end itemize