docs: doxygen 11 adds extra space in URL

[hyoklee]

Note: 1_14 doesn't use alias.

<li><a href="https://hdfgroup.github.io/hdf5/develop /index.html">HDF5 <code>develop</code> branch (this site)</a></li>
<li><a href="https://hdfgroup.github.io/hdf5/v1_14/index.html">HDF5 1.14.x</a></li>
<li><a href="https://docs.hdfgroup.org/hdf5 /v1_12/index.html">HDF5 1.12.x</a></li>
<li><a href="https://docs.hdfgroup.org/hdf5 /v1_10/index.html">HDF5 1.10.x</a></li>
<li><a href="https://docs.hdfgroup.org/hdf5 /v1_8/index.html">HDF5 1.8.x</a></li>