doc: reduce features tables column width

The font size of the header row is reduced in order to shrink
the column size of the tables.
It is required for the NICs features table which is too large to fit
in the page width.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>

doc/guides/conf.py

@@ -310,7 +310,7 @@ def print_table_css(outfile, table_id):
          text-align: center;
       }
       table#idx th {
-         font-size: 80%;
+         font-size: 72%;
          white-space: pre-wrap;
          vertical-align: top;
          padding: 0.5em 0;