bitfield_gen: remove manual table of contents

Remove manual table of contents for rendering on the docsite, which will
provide an automatic TOC.

Signed-off-by: Gerwin Klein <gerwin.klein@proofcraft.systems>

tools/bitfield_gen.md

@@ -5,29 +5,6 @@
 
 # Bitfield Generator Manual
 
-- [Introduction](#introduction)
-- [Bit Field Generator by Example](#bit-field-generator-by-example)
-  - [Blocks](#blocks)
-  - [Field High](#field-high)
-  - [Visible Field Order](#visible-field-order)
-  - [Tagged Unions](#tagged-unions)
-  - [Advanced Tag Fields](#advanced-tag-fields)
-    - [Tag Slices](#tag-slices)
-    - [Masks](#masks)
-  - [Raw Value Access](#raw-value-access)
-  - [Architecture Parameters and Canonical Pointers](#architecture-parameters-and-canonical-pointers)
-- [Syntax Reference](#syntax-reference)
-  - [Lexical Structure](#lexical-structure)
-  - [Syntactic Structure](#syntactic-structure)
-  - [Restrictions](#restrictions)
-- [Correctness](#correctness)
-- [Limitations](#limitations)
-- [Command Line](#command-line)
-  - [Usage](#usage)
-  - [Options](#options)
-  - [seL4 build](#sel4-build)
-
-
 ## Introduction
 
 The tool `bitfield_gen.py` in the `seL4/tools/` directory generates bitfield