readme: remove size in badges

Author: jcarpent

README.md

@@ -5,7 +5,7 @@ PyCppAD — Python bindings for CppAD Automatic Differentiation library
     <a href="https://opensource.org/licenses/BSD-3-Clause"><img src="https://img.shields.io/badge/License-BSD%203--Clause-green.svg" alt="License"/></a>
     <a href="https://anaconda.org/conda-forge/pycppad"><img src="https://img.shields.io/conda/dn/conda-forge/pycppad.svg" alt="Conda Downloads"/></a>
     <a href="https://anaconda.org/conda-forge/pycppad"><img src="https://img.shields.io/conda/vn/conda-forge/pycppad.svg" alt="Conda Version"/></a>
-    <a href="https://badge.fury.io/py/pycppad"><img src="https://badge.fury.io/py/pycppad.svg" alt="PyPI version" height="18"></a>
+    <a href="https://badge.fury.io/py/pycppad"><img src="https://badge.fury.io/py/pycppad.svg" alt="PyPI version"></a>
 </p>
 
 **PyCppAD** is an open source framework which provides bindings for the CppAD Automatic Differentiation([CppAD](https://coin-or.github.io/CppAD/doc/cppad.htm)) C++ library in Python.