Update README.md (#9078)

remove dollar sign for easier copying

src/README.md

diff --git a/src/README.md b/src/README.md
index 51d9e2f..9db40fd 100644
--- a/src/README.md
+++ b/src/README.md
@@ -19,7 +19,7 @@
 
 On Ubuntu/Debian, you can install them with:
 
-    $ sudo apt-get install autoconf automake libtool curl make g++ unzip
+    sudo apt-get install autoconf automake libtool curl make g++ unzip
 
 On other platforms, please use the corresponding package managing tool to
 install them before proceeding.