add -Wd

https://mail.python.org/pipermail/python-dev/2010-April/099116.html

> -Wd enables all warnings.  It adds 'd' to sys.warnoptions, which in turn
> adds a new first entry to _warnings.filters which matches all warnings and
> enables the "default" behavior, which is to show it once per execution of
> the Python interpreter.

pytest options:

> reporting:
> ...
> -r chars              show extra test summary info as specified by chars:
> (f)ailed, (E)rror, (s)kipped, (x)failed, (X)passed, (p)assed, (P)assed with
> output, (a)ll except passed (p/P), or (A)ll. (w)arnings are enabled by default
> (see --disable-warnings), 'N' can be used to reset the list. (default: 'fE').

pyproject.toml

@@ -42,7 +42,8 @@ ignore = [
 minversion = "6.0"
 xfail_strict = true
 addopts = [
-    "-r a",
+    "-ra",
+    "-Wd",
     "--cov=pyhf",
     "--cov-branch",
     "--showlocals",