snippet/_Noreturn: Fix typo

[Akim Demaille]

From a report by Christopher Nielsen <mascguy@github.com> about Bison (which 
uses an almost verbatim copy of this snippet).

<https://trac.macports.org/ticket/59927#comment:59>
<https://trac.macports.org/ticket/59927#comment:62>

Cheers!

commit 964ce0a92b9ba87afe7787dc0fd5d1e1abe7214c
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Thu Aug 12 09:30:41 2021 +0200

    snippet/_Noreturn: Fix typo
    
    * lib/_Noreturn.h: Fix spelling of 4.

diff --git a/ChangeLog b/ChangeLog
index 037fa7da4..b8a93468d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2021-08-12  Akim Demaille  <akim@lrde.epita.fr>
+
+       snippet/_Noreturn: Fix typo
+       * lib/_Noreturn.h: Fix spelling of 4.
+
 2021-08-11  Paul Eggert  <eggert@cs.ucla.edu>
 
        dynarray: merge from glibc
diff --git a/lib/_Noreturn.h b/lib/_Noreturn.h
index cb72f2620..6fed3c797 100644
--- a/lib/_Noreturn.h
+++ b/lib/_Noreturn.h
@@ -29,7 +29,7 @@
 # elif ((!defined __cplusplus || defined __clang__) \
         && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \
             || (!defined __STRICT_ANSI__ \
-                && (__4 < __GNUC__ + (7 <= __GNUC_MINOR__) \
+                && (4 < __GNUC__ + (7 <= __GNUC_MINOR__) \
                     || (defined __apple_build_version__ \
                         ? 6000000 <= __apple_build_version__ \
                         : 3 < __clang_major__ + (5 <= __clang_minor__))))))