doc: make strike line transparent to make text in pre more readable

W3C Candidate Recommendation 1 August 2013
https://www.w3.org/TR/css-text-decor-3/#text-decoration-color-property
Works at least in Mozilla Firefox.


git-svn-id: https://svn.osgeo.org/grass/grass/trunk@69731 15284696-431f-4ddb-bdfa-cd5b030d7da7

man/grassdocs.css

@@ -229,3 +229,8 @@ table.compact tr:nth-child(odd) {
 table.compact tr:nth-child(even) {
     background: #FFF;
 }
+
+/* soft strike through so that we can still see the text */
+s {
+    text-decoration-color: rgba(0, 0, 0, 0.53);
+}