ch04: Remove bash symbol from comments

ch04.asciidoc

@@ -603,11 +603,11 @@ include::code/ec-math.py[]
 .Installing the Python ECDSA library and running the ec_math.py script
 ====
 ----
-$ # Install Python PIP package manager
+# Install Python PIP package manager
 $ sudo apt-get install python-pip
-$ # Install the Python ECDSA library
+# Install the Python ECDSA library
 $ sudo pip install ecdsa
-$ # Run the script
+# Run the script
 $ python ec-math.py
 Secret:  38090835015954358862481132628887443905906204995912378278060168703580660294000
 EC point: (70048853531867179489857750497606966272382583471322935454624595540007269312627, 105262206478686743191060800263479589329920209527285803935736021686045542353380)
@@ -723,13 +723,13 @@ The example code must be compiled using a pass:[C++] compiler and linked against
 ====
 [source,bash]
 ----
-$ # Compile the code with g++
+# Compile the code with g++
 $ g++ -o vanity-miner vanity-miner.cpp $(pkg-config --cflags --libs libbitcoin)
-$ # Run the example
+# Run the example
 $ ./vanity-miner
 Found vanity address! 1KiDzkG4MxmovZryZRj8tK81oQRhbZ46YT
 Secret: 57cc268a05f83a23ac9d930bc8565bac4e277055f4794cbd1a39e5e71c038f3f
-$ # Run it again for a different result
+# Run it again for a different result
 $ ./vanity-miner
 Found vanity address! 1Kidxr3wsmMzzouwXibKfwTYs5Pau8TUFn
 Secret: 7f65bbbbe6d8caae74a0c6a0d2d7b5c6663d71b60337299a1a2cf34c04b2a623