Update shell format in installation instructions.

src/README.md

diff --git a/src/README.md b/src/README.md
index 007deb3..78d6bb5 100644
--- a/src/README.md
+++ b/src/README.md
@@ -40,22 +40,21 @@
 have also cloned the submodules and generated the configure script (skip this
 if you are using a release .tar.gz or .zip package):
 
-```shell
     git clone https://github.com/protocolbuffers/protobuf.git
     cd protobuf
     git submodule update --init --recursive
     ./autogen.sh
-```
+
 To build and install the C++ Protocol Buffer runtime and the Protocol
 Buffer compiler (protoc) execute the following:
 
-```shell
+
      ./configure
      make
      make check
      sudo make install
      sudo ldconfig # refresh shared library cache.
-```
+
 If "make check" fails, you can still install, but it is likely that
 some features of this library will not work correctly on your system.
 Proceed at your own risk.
@@ -123,15 +122,15 @@
 For a Mac system, Unix tools are not available by default. You will first need
 to install Xcode from the Mac AppStore and then run the following command from
 a terminal:
-```shell
+
     sudo xcode-select --install
-```shell
+
 To install Unix tools, you can install "port" following the instructions at
 https://www.macports.org . This will reside in /opt/local/bin/port for most
 Mac installations.
-```shell
+
     sudo /opt/local/bin/port install autoconf automake libtool
-```
+
 Then follow the Unix instructions above.
 
 **Note for cross-compiling**