docs(gpu): revise driver section headers

Author: dsloanm

explanation/gpus/driver.md

@@ -1,5 +1,7 @@
 (driver)=
-# Driver auto-install
+# GPU driver installation and management
+
+## Auto-install
 
 Charmed HPC installs GPU drivers when the `slurmd` charm is deployed on a compute node equipped with a supported Nvidia GPU. Driver detection is performed via the API for [`ubuntu-drivers-common`](https://documentation.ubuntu.com/server/how-to/graphics/install-nvidia-drivers/#the-recommended-way-ubuntu-drivers-tool), a package which examines node hardware, determines appropriate third-party drivers and recommends a set of driver packages that are installed from the Ubuntu repositories.