Update the version header in the current fallback file to 2.0.0

The upcoming fallback rebuild will automatically generate this new format.

Follow-up to 24725, due to breaking changes in 24679, 24600, and 22759.

src/or/fallback_dirs.inc

@@ -1,5 +1,5 @@
 /* type=fallback */
-/* version=1.0.0 */
+/* version=2.0.0 */
 /* Whitelist & blacklist excluded 1326 of 1513 candidates. */
 /* To comment-out entries in this file, use C comments, and add * to the start of each line. (stem finds fallback entries using " at the start of a line.) */
 /* Checked IPv4 DirPorts served a consensus within 15.0s. */