images: use smaller optimized files to reduce pdf file size

Author: entorb

chapters/hpmor-chapter-122.tex

@@ -523,7 +523,7 @@ \chapter{Something to Protect: Hermione Granger}
 \vspace*{\fill}
 {
 \begin{center}
-\includegraphics[scale=0.125]{images/Deathly_Hallows_Sign.png}
+\includegraphics[scale=0.125]{images/Deathly_Hallows_Sign.pdf}
 \end{center}
 }
 \vspace*{\fill}

ebook/1_latex2html.py

@@ -243,7 +243,7 @@ def tex2html(s: str) -> str:
         flags=re.DOTALL | re.IGNORECASE,
     )
 
-    was = "{\n\\begin{center}\n\\includegraphics[scale=0.125]{images/Deathly_Hallows_Sign.png}\n\\end{center}\n}"
+    was = "{\n\\begin{center}\n\\includegraphics[scale=0.125]{images/Deathly_Hallows_Sign.pdf}\n\\end{center}\n}"
     s = s.replace(was, "")
 
     # paper notes in Chapter 13

images/Deathly_Hallows_Sign.pdf

@@ -23,7 +23,7 @@
 
 \Large\MakeUppercase{and the Methods of Rationality} %
 
-\includegraphics[scale=0.5]{images/bubble0.png}
+\includegraphics[scale=0.5]{images/bubble0.jpg}
 
 \Large BY \vspace*{.25cm}