gitweb: Do not use absolute font sizes

David Kågedal proposed that gitweb should explicitely request
being somewhat smaller than normal, because it has good use for
long lines. However gitweb presents a table with several
columns, so having wider line is OK for it. Therefore explicit
'font-size: small' would make sense.  Apparently many people on
the list seem to agree with him.

Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.css

@@ -1,5 +1,6 @@
 body {
 	font-family: sans-serif;
+	font-size: small;
 	border: solid #d9d8d1;
 	border-width: 1px;
 	margin: 10px;