sysctl: documentation: fix table format warning

Fix malformed table warning in sysctl documentation:
(don't use ':'s)

Documentation/admin-guide/sysctl/kernel.rst:798: WARNING: Malformed table.
Text in column margin in table line 7.

=====  ============================================
bit 0  print all tasks info
bit 1  print system memory info
bit 2  print timer info
bit 3  print locks info if ``CONFIG_LOCKDEP`` is on
bit 4  print ftrace buffer
bit 5: print all printk messages in buffer
bit 6: print all CPUs backtrace (if available in the arch)

Link: https://lkml.kernel.org/r/20220109055635.6999-1-rdunlap@infradead.org
Fixes: 934d51c ("docs: sysctl/kernel: add missing bit to panic_print")
Fixes: addc649 ("panic: add option to dump all CPUs backtraces in panic_print")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

Documentation/admin-guide/sysctl/kernel.rst

@@ -795,8 +795,8 @@ bit 1  print system memory info
 bit 2  print timer info
 bit 3  print locks info if ``CONFIG_LOCKDEP`` is on
 bit 4  print ftrace buffer
-bit 5: print all printk messages in buffer
-bit 6: print all CPUs backtrace (if available in the arch)
+bit 5  print all printk messages in buffer
+bit 6  print all CPUs backtrace (if available in the arch)
 =====  ============================================
 
 So for example to print tasks and memory info on panic, user can::