Start cleaning up docs

Author: matthewdouglas

docs/source/_toctree.yml

@@ -2,18 +2,15 @@
   sections:
   - local: index
     title: bitsandbytes
-  - local: quickstart
-    title: Quickstart
   - local: installation
     title: Installation
-- title: Guides
+  - local: quickstart
+    title: Quickstart
+
+- title: Usage Guides
   sections:
   - local: optimizers
     title: 8-bit optimizers
-  - local: algorithms
-    title: Algorithms
-  - local: non_cuda_backends
-    title: Non-CUDA compute backends
   - local: fsdp_qlora
     title: FSDP-QLoRA
   - local: integrations