docs/style_guide: revert stance on non-type template args

Reverts our stance on non-type template argument style to be
consistent with the naming standard applied to other varibles whose
value is fixed for the duration of the program, namely kCamelCase.

Change-Id: If3309ca63199cebaf24d058b82296000abf05a45
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39660
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
diff --git a/docs/style_guide.rst b/docs/style_guide.rst
index 1087c51..3d04581 100644
--- a/docs/style_guide.rst
+++ b/docs/style_guide.rst
@@ -250,15 +250,18 @@
   * If private code must be exposed in a header file, it must be in a namespace
     nested under ``pw``. The namespace may be named for its subsystem or use a
     name that designates it as private, such as ``internal``.
-  * Template arguments for non-type names (e.g. ``template <int foo_bar>``)
-    should follow the variable naming convention, which means snake case (e.g.
-    ``foo_bar``). This matches the Google C++ style, however the wording in the
-    official style guide isn't explicit and could be interpreted to use
-    ``kFooBar`` style naming. Wide practice establishes that the naming
-    convention is ``snake_case``, and so that is the style we use in Pigweed.
+  * Template arguments for non-type names (e.g. ``template <int kFooBar>``)
+    should follow the constexpr and const variable Google naming convention,
+    which means k prefixed camel case (e.g.
+    ``kCamelCase``). This matches the Google C++ style for variable naming,
+    however the wording in the official style guide isn't explicit for template
+    arguments and could be interpreted to use ``foo_bar`` style naming.
+    For consistency with other variables whose value is always fixed for the
+    duration of the program, the naming convention is ``kCamelCase``, and so
+    that is the style we use in Pigweed.
 
     **Note:** At time of writing much of Pigweed incorrectly follows the
-    ``kCamelCase`` naming for non-type template arguments. This is a bug that
+    ``snake_case`` naming for non-type template arguments. This is a bug that
     will be fixed eventually.
 
 **C code**