Add space before backquote

[greg0ire]

According to the RST docs,

[inline markup] it must be separated from surrounding text by non-word
characters. Use a backslash escaped space to work around that: thisis\ one\ word.

Because we were missing a space before backquotes here, the links were not rendered. Escaping the space allow not to actually produce a space in the output.

See https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#inline-markup

[greg0ire]

Note that although doctrine/rst-parser cares about this, the Parser used by Github does not seem to care, hence, no diff.

[greg0ire]

Thanks @linawolf for the solution!