Reword note on missing CJK fonts

Use past tense as the fonts can be installed after the fact.
Add suggestion to install "Noto Sans CJK" and "Noto Serif CJK"
font families. ("Noto Serif CJK" is optional.)

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/dfefa601-c58d-c86c-953f-5e4454db9409@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sphinx/kerneldoc-preamble.sty

@@ -205,9 +205,16 @@
     %% CJK chapters can be ignored.
     \newcommand{\kerneldocBeginSC}[1]{%
 	%% Put a note on missing CJK fonts in place of zh_CN translation.
-	\begin{sphinxadmonition}{note}{Note:}
-	    ``Noto Sans CJK'' fonts are not found while building this PDF\@.
-	    Translations of zh\_CN, zh\_TW, ko\_KR, and ja\_JP are skipped.
+	\begin{sphinxadmonition}{note}{Note on missing fonts:}
+	    Translations of Simplified Chinese (zh\_CN), Traditional Chinese
+	    (zh\_TW), Korean (ko\_KR), and Japanese (ja\_JP) were skipped
+	    due to the lack of suitable font families.
+
+	    If you want them, please install ``Noto Sans CJK'' font families
+	    by following instructions from
+	    \sphinxcode{./scripts/sphinx-pre-install}.
+	    Having optional ``Noto Serif CJK'' font families will improve
+	    the looks of those translations.
 	\end{sphinxadmonition}}
     \newcommand{\kerneldocEndSC}{}
     \newcommand{\kerneldocBeginTC}[1]{}