docs: Order the example sections manually (#1152)

Fix part of #1019

✅ We can set an explicit order for the subsections (the categories of
examples):
```python
# list of examples in explicit order
subsections_order = [
    "../examples/getting_started",
    "../examples/model_evaluation",
]

sphinx_gallery_conf = {
    # ...
    "subsection_order": ExplicitOrder(subsections_order),  # sorting gallery subsections,
    # ...
}
```

❌ Inside a subsection, we can sort the examples by example title:
```python
sphinx_gallery_conf = {
    # ...
    "within_subsection_order": "ExampleTitleSortKey",
    # ...
}
```
but I can't set an explicit order myself for the examples in
`getting_started` and in `model_evaluation`.
This will be for another PR.

sphinx/conf.py

@@ -61,18 +61,12 @@
 ]
 
 # list of examples in explicit order
-examples_ordered = [
+subsections_order = [
     "../examples/getting_started",
-    "../examples/getting_started/plot_quick_start",
-    "../examples/getting_started/plot_skore_product_tour",
-    "../examples/getting_started/plot_working_with_projects",
-    "../examples/getting_started/plot_tracking_items",
     "../examples/model_evaluation",
-    "../examples/model_evaluation/plot_train_test_split",
-    "../examples/model_evaluation/plot_cross_validate",
 ]
 
-
+# Augment the dpi of matplotlib figures in Sphinx examples
 # https://sphinx-gallery.github.io/stable/advanced.html#resetting-before-each-example
 def reset_mpl(gallery_conf, fname):
     import matplotlib
@@ -84,8 +78,9 @@ def reset_mpl(gallery_conf, fname):
 sphinx_gallery_conf = {
     "examples_dirs": "../examples",  # path to example scripts
     "gallery_dirs": "auto_examples",  # path to gallery generated output
-    "subsection_order": ExplicitOrder(examples_ordered),
-    "within_subsection_order": "FileNameSortKey",  # See https://sphinx-gallery.github.io/stable/configuration.html#sorting-gallery-examples for alternatives
+    "subsection_order": ExplicitOrder(subsections_order),  # sorting gallery subsections,
+    # see https://sphinx-gallery.github.io/stable/configuration.html#sub-gallery-order
+    "within_subsection_order": "ExampleTitleSortKey",  # See https://sphinx-gallery.github.io/stable/configuration.html#sorting-gallery-examples for alternatives
     "show_memory": False,
     "write_computation_times": False,
     "reference_url": {