fixup! fixup! ENH: revive and update yt.funcs.matplotlib_style_contex…

…t context manager

yt/funcs.py

@@ -993,23 +993,20 @@ def get_brewer_cmap(cmap):
     return bmap.get_mpl_colormap(N=cmap[2])
 
 
-def matplotlib_style_context(style=None, after_reset=False):
+def matplotlib_style_context(style="yt.default", after_reset=False):
     """Returns a context manager for controlling matplotlib style.
 
     Arguments are passed to matplotlib.style.context() if specified. Defaults
-    to setting "yt.default" style, after resetting to the default config parameters.
+    to setting yt's "yt.default" style, after resetting to the default config parameters.
     """
     # FUTURE: this function should be deprecated in favour of matplotlib.style.context
     # after support for matplotlib 3.6 and older versions is dropped.
     import matplotlib.style
 
     from yt.visualization._commons import MPL_VERSION
 
-    if style is None:
-        if MPL_VERSION >= Version("3.7"):
-            style = "yt.default"
-        else:
-            style = importlib_resources.files("yt") / "default.mplstyle"
+    if style == "yt.default" and MPL_VERSION < Version("3.7"):
+        style = importlib_resources.files("yt") / "default.mplstyle"
 
     return matplotlib.style.context(style, after_reset=after_reset)