DOC: tutorials/introduction: shorten title to just Tutorial

There is just one tutorial so a longer title just wastes real estate
in the navigation bar. Even expanding the content of the tutorial to
cover more concepts I do not see it growing to a length warranting
splitting it into multiple pages.

Author: dnicolodi

docs/tutorials/introduction.rst

@@ -2,11 +2,11 @@
 ..
 .. SPDX-License-Identifier: MIT
 
-.. _tutorial-introduction:
+.. _tutorial:
 
-******************************************************
-Introduction to Python packaging with ``meson-python``
-******************************************************
+********
+Tutorial
+********
 
 If you are new to Python packaging, don't worry!