syntax-check: do not enforce ChangeLog syntax

Our last conforming ChangeLog was removed from git in 2009 by:
commit 27b175b9
    generate ChangeLog from git logs into distribution tarball

Ten years later, it reappeared in:
commit ce97c33a
    maint: Stop generating ChangeLog from git
which does not have a single line complying to this syntax
check rule.

At some point between the two commits VC_LIST_EXCEPT gained
a default exception for ChangeLog and it did not seem to be
overriden anywhere.

Just remove the rule.
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

build-aux/syntax-check.mk

@@ -1616,13 +1616,6 @@ sc_prohibit_dirent_without_use:
 sc_prohibit_xfreopen_without_use:
 	@h='xfreopen.h' re='\<xfreopen *\(' $(_sc_header_without_use)
 
-# Each nonempty ChangeLog line must start with a year number, or a TAB.
-sc_changelog:
-	@prohibit='^[^12	]'					\
-	in_vc_files='^ChangeLog$$'					\
-	halt='found unexpected prefix in a ChangeLog'			\
-	  $(_sc_search_regexp)
-
 # Ensure that each .c file containing a "main" function also
 # calls bindtextdomain.
 sc_bindtextdomain: