DOC: Cleanup scales examples

- Remove https://matplotlib.org/3.9.3/gallery/scales/log_bar.html
  The only scale-related aspect of the example is `ax.set_yscale("log")`.
  That's not something we need an extra example for. The scale works for
  all data content. We don't need to show that it also works for bars.
  Even worse, the example creates grouped bars, which require extra code
  and therefore distract from the scale aspect.
- Rename some example titles "Demo" -> "scale"

Author: timhoffm

galleries/examples/scales/asinh_demo.py

@@ -1,7 +1,7 @@
 """
-============
-Asinh Demo
-============
+===========
+Asinh scale
+===========
 
 Illustration of the `asinh <.scale.AsinhScale>` axis scaling,
 which uses the transformation

galleries/examples/scales/log_bar.py

@@ -1,7 +1,7 @@
 """
-================
-Logit Demo
-================
+===========
+Logit scale
+===========
 
 Examples of plots with logit axes.
 """

galleries/examples/scales/logit_demo.py

@@ -1,7 +1,7 @@
 """
-======
-Scales
-======
+===============
+Scales overview
+===============
 
 Illustrate the scale transformations applied to axes, e.g. log, symlog, logit.