[llvm] [NFC] Remove explicit bitcode enumeration from BitCodeFormat.rst (PR #102618)

[Stephen Tozer via llvm-commits]

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@@ -1006,93 +1006,29 @@ number of values representing the bytes of a null-terminated string. For
 attributes with a string argument (code 4), the *value* value is similarly a
 variable number of values representing the bytes of a null-terminated string.
 
-The integer codes are mapped to well-known attributes as follows.
+The integer codes are mapped to well-known attributes as described in the
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SLTozer wrote:

```suggestion
The integer codes are mapped to attributes as described in the
```
While we're looking at this, what does "well-known" mean in this context?

https://github.com/llvm/llvm-project/pull/102618