Remove the grave accent (`) from the default word regex

Catching typos that contain a grave accent (`) is a niche. I bet we miss
more typos in Markdown files than we detect typos containing a grave
accent (`).

codespell_lib/_codespell.py

@@ -28,7 +28,7 @@
 # autogenerated by setuptools_scm
 from ._version import __version__ as VERSION  # type: ignore  # noqa: N812
 
-word_regex_def = "[\\w\\-'’`]+"
+word_regex_def = r"[\w\-'’]+"
 # While we want to treat characters like ( or " as okay for a starting break,
 # these may occur unescaped in URIs, and so we are more restrictive on the
 # endpoint.  Emails are more restrictive, so the endpoint remains flexible.

codespell_lib/data/dictionary.txt

@@ -11479,8 +11479,8 @@ cought->caught, cough, fought,
 coul->could
 could'nt->couldn't
 could't->couldn't
+coulden't->couldn't
 couldent->couldn't
-coulden`t->couldn't
 couldn->could, couldn't,
 couldn;t->couldn't
 couldnt'->couldn't
@@ -47403,8 +47403,8 @@ woudl->would
 woudn't->wouldn't
 would'nt->wouldn't
 would't->wouldn't
+woulden't->wouldn't
 wouldent->wouldn't
-woulden`t->wouldn't
 wouldn;t->wouldn't
 wouldnt'->wouldn't
 wouldnt->wouldn't