Bump debhelper compat level from 12 to 13

- debian/rules: Drop --fail-missing argument to dh_missing, which is
  now the default.

Changes-By: lintian-brush
Fixes: lintian: package-uses-old-debhelper-compat-version
See-also: https://lintian.debian.org/tags/package-uses-old-debhelper-compat-version.html

debian/control

@@ -14,7 +14,7 @@ Build-Depends:
  bsdextrautils <!nocheck> | bsdmainutils (<< 12) <!nocheck>,
  ca-certificates,
  cpio,
- debhelper-compat (= 12),
+ debhelper-compat (= 13),
  dh-exec (>= 0.23~),
  docbook-xml <!nodoc>,
  docbook-xsl <!nodoc>,

debian/rules

@@ -68,9 +68,6 @@ override_dh_install:
 	:
 	dh_install
 
-override_dh_missing:
-	dh_missing --fail-missing
-
 override_dh_makeshlibs:
 	# this is an LD_PRELOAD, not a real shared library
 	dh_makeshlibs -Xinstalled-tests/ostree/libreaddir-rand.so