[clang] [NFC][analyzer][docs] Remove some orphaned images (PR #122249)

[Balazs Benics via cfe-commits]

steakhal wrote:

Its usually good practice to refer to the last commit where the dead resources become dead.
You can use the git log -S to find out about the commits the thing is mentioned.

Example: `git log -Sexample_custom_assert -- clang/www/analyzer/`, will mention:
```
61a76f58ebf161c739fb196d56c1899735c7cea8 [clang][analyzer][doc] Migrate ClangSA www FAQ section (#112831)
```

You can get a better understanding if the drop was intentional or accidental.

https://github.com/llvm/llvm-project/pull/122249