Remove hardcoded Python/NumPy versions in MAINTENANCE.md docs

Author: weiji14

MAINTENANCE.md

@@ -78,8 +78,8 @@ There are 9 configuration files located in `.github/workflows`:
 
    This is run on every commit to the *master* and Pull Request branches.
    It is also scheduled to run daily on the *master* branch.
-   In draft Pull Requests, only two jobs on Linux (Python 3.7 / NumPy 1.17 and
-   Python 3.9/ NumPy 1.20) are triggered to save on Continuous Integration
+   In draft Pull Requests, only two jobs on Linux (minimum NEP29 Python/NumPy versions
+   and latest Python/NumPy versions) are triggered to save on Continuous Integration
    resources.
 
 3. `ci_docs.yml` (Build documentation on Linux/macOS/Windows)