d/control: depend on libtiff 4.2.0+

Previous Debian package introduced a breaking change without a version
bump, making megapixels crash. Make sure we use a proper version for
building the package.

debian/control

@@ -6,7 +6,7 @@ Uploaders: Federico Ceratto <federico@debian.org>, Arnaud Ferraris <arnaud.ferra
 Build-Depends:
  debhelper-compat (= 13),
  libgtk-3-dev,
- libtiff-dev,
+ libtiff-dev (>= 4.2.0),
  meson,
 Standards-Version: 4.5.1
 Homepage: https://git.sr.ht/~martijnbraam/megapixels