Documentation: fix core_pattern max length

The buffer size for core_pattern is 128, but one character is used for
terminating null byte, so the actual limit is 127:

    # printf '%0999d' > /proc/sys/kernel/core_pattern
    # tr -d '\n' < /proc/sys/kernel/core_pattern | wc -c
    127

Signed-off-by: Jakub Wilk <jwilk@jwilk.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sysctl/kernel.txt

@@ -196,7 +196,7 @@ CAP_LAST_CAP from the kernel.
 core_pattern:
 
 core_pattern is used to specify a core dumpfile pattern name.
-. max length 128 characters; default value is "core"
+. max length 127 characters; default value is "core"
 . core_pattern is used as a pattern template for the output filename;
   certain string patterns (beginning with '%') are substituted with
   their actual values.