Update d/watch to version 4

debian/changelog

@@ -1,8 +1,9 @@
 cmake (3.21.2-2) UNRELEASED; urgency=medium
 
   * Migrate emacsen helpers to dh_elpa (Closes: #802915)
+  * Update d/watch to version 4
 
- -- Timo Röhling <roehling@debian.org>  Fri, 17 Sep 2021 14:42:17 +0200
+ -- Timo Röhling <roehling@debian.org>  Fri, 17 Sep 2021 15:29:01 +0200
 
 cmake (3.21.2-1) unstable; urgency=medium
 

debian/watch

@@ -1,6 +1,3 @@
-version=3
-
-# Track CMake 2.6.x releases including RCs
-opts="uversionmangle=s/-[Rr][Cc]-?(\d+)/~rc$1/i" \
-    https://cmake.org/files/v([\d.]+)/ \
-    cmake-([\d.]+(?i:-RC-?\d+)?).tar.gz
+version=4
+opts="uversionmangle=s/-RC-?/~rc/i" \
+  https://cmake.org/files/v([\d.]+)/ cmake-([\d.]+(?i:-RC-?\d+)?)@ARCHIVE_EXT@