Update kernel version to 6.8 in header constant tests

This patch updates the kernel version in the tests tst-mman-consts.py,
tst-mount-consts.py and tst-pidfd-consts.py to 6.8.  (There are no new
constants covered by these tests in 6.8 that need any other header
changes.)

Tested with build-many-glibcs.py.

sysdeps/unix/sysv/linux/tst-mman-consts.py

@@ -33,7 +33,7 @@ def main():
                         help='C compiler (including options) to use')
     args = parser.parse_args()
     linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc)
-    linux_version_glibc = (6, 7)
+    linux_version_glibc = (6, 8)
     sys.exit(glibcextract.compare_macro_consts(
         '#define _GNU_SOURCE 1\n'
         '#include <sys/mman.h>\n',

sysdeps/unix/sysv/linux/tst-mount-consts.py

@@ -39,10 +39,10 @@ def main():
         sys.exit (77)
 
     linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc)
-    # Constants in glibc were updated to match Linux v6.7.  When glibc
+    # Constants in glibc were updated to match Linux v6.8.  When glibc
     # constants are updated this value should be updated to match the
     # released kernel version from which the constants were taken.
-    linux_version_glibc = (6, 7)
+    linux_version_glibc = (6, 8)
     def check(cte, exclude=None):
         return glibcextract.compare_macro_consts(
                 '#include <sys/mount.h>\n',

sysdeps/unix/sysv/linux/tst-pidfd-consts.py

@@ -39,7 +39,7 @@ def main():
         sys.exit (77)
 
     linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc)
-    linux_version_glibc = (6, 7)
+    linux_version_glibc = (6, 8)
     sys.exit(glibcextract.compare_macro_consts(
                 '#include <sys/pidfd.h>\n',
                 '#include <asm/fcntl.h>\n'