[LaTeX] use "regular" variant of light bulb for hint/tip

sphinx/texinputs/sphinx.sty

@@ -772,7 +772,7 @@
   % \sphinxdotitlerowwithicon in sphinxlatexadmonitions.sty).  If user sets a
   % title-icon key to some LaTeX code of their own, of course \spx@faIcon is
   % not executed and the inserted space will thus be there, as expected.
-  \let\spx@faIcon\@gobbletwo
+  \newcommand\spx@faIcon[3][]{}%
 }
 
 % Now use the above colours as default settings, following the choices
@@ -809,8 +809,8 @@
 % is absent, it is *not* a public macro to be used in custom user-level
 % usage of the title-icon keys below!
   div.note_title-icon      =\spx@faIcon{info-circle},
-  div.hint_title-icon      =\spx@faIcon{lightbulb},
-  div.tip_title-icon       =\spx@faIcon{lightbulb},
+  div.hint_title-icon      =\spx@faIcon[regular]{lightbulb},
+  div.tip_title-icon       =\spx@faIcon[regular]{lightbulb},
   div.seealso_title-icon   =\spx@faIcon{share},
   div.important_title-icon =\spx@faIcon{pause-circle},
   div.caution_title-icon   =\spx@faIcon{radiation},