Use version 5.7's docs instead of 5.6, since that's the most up to da…

…te version of MySQL that we support.

website/docs/r/sql_database.html.markdown

@@ -46,14 +46,14 @@ The following arguments are supported:
 
 * `charset` - (Optional) The charset value. See MySQL's [Supported Character
     Sets and
-    Collations](https://dev.mysql.com/doc/refman/5.6/en/charset-charsets.html)
+    Collations](https://dev.mysql.com/doc/refman/5.7/en/charset-charsets.html)
     and PostgreSQL's [Character Set
     Support](https://www.postgresql.org/docs/9.6/static/multibyte.html)
     for more details and supported values.
 
 * `collation` - (Optional) The collation value. See MySQL's [Supported Character
     Sets and
-    Collations](https://dev.mysql.com/doc/refman/5.6/en/charset-charsets.html)
+    Collations](https://dev.mysql.com/doc/refman/5.7/en/charset-charsets.html)
     and PostgreSQL's [Collation
     Support](https://www.postgresql.org/docs/9.6/static/collation.html) for
     more details and supported values.