docs: clean up sysctl/kernel: titles, version

This cleans up a few titles with extra colons, and removes the
reference to kernel 2.2. The docs don't yet cover *all* of 5.10 or
5.11, but I think they're close enough. Most entries are documented,
and have been checked against current kernels.
Signed-off-by: Stephen Kitt <steve@sk2.org>
Link: https://lore.kernel.org/r/20201208074922.30359-1-steve@sk2.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/sysctl/kernel.rst

@@ -14,7 +14,7 @@ For general info and legal blurb, please look in :doc:`index`.
 ------------------------------------------------------------------------------
 
 This file contains documentation for the sysctl files in
-``/proc/sys/kernel/`` and is valid for Linux kernel version 2.2.
+``/proc/sys/kernel/``.
 
 The files in this directory can be used to tune and monitor
 miscellaneous and general things in the operation of the Linux
@@ -1095,8 +1095,8 @@ Enables/disables scheduler statistics. Enabling this feature
 incurs a small amount of overhead in the scheduler but is
 useful for debugging and performance tuning.
 
-sched_util_clamp_min:
-=====================
+sched_util_clamp_min
+====================
 
 Max allowed *minimum* utilization.
 
@@ -1106,8 +1106,8 @@ It means that any requested uclamp.min value cannot be greater than
 sched_util_clamp_min, i.e., it is restricted to the range
 [0:sched_util_clamp_min].
 
-sched_util_clamp_max:
-=====================
+sched_util_clamp_max
+====================
 
 Max allowed *maximum* utilization.
 
@@ -1117,8 +1117,8 @@ It means that any requested uclamp.max value cannot be greater than
 sched_util_clamp_max, i.e., it is restricted to the range
 [0:sched_util_clamp_max].
 
-sched_util_clamp_min_rt_default:
-================================
+sched_util_clamp_min_rt_default
+===============================
 
 By default Linux is tuned for performance. Which means that RT tasks always run
 at the highest frequency and most capable (highest capacity) CPU (in