docs: update vulnerability scanning table to use unicode checkmarks

Author: Pouyanpi

docs/evaluation/llm-vulnerability-scanning.md

@@ -22,10 +22,9 @@ The table below summarizes what is included in each configuration:
 
 |                                                     | `bare_llm` | `with_gi`          | `with_gi_dr`       | `with_gi_dr_mo`    |
 |-----------------------------------------------------|------------|--------------------|--------------------|--------------------|
-| General Instructions                                | x          | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: |
-| Dialog Rails <br/> (refuse unwanted topics)         | x          | x                  | :heavy_check_mark: | :heavy_check_mark: |
-| Moderation Rails <br/> (input/output self-checking) | x          | x                  | x                  | :heavy_check_mark: |
-
+| General Instructions                                | x          | ✓                  | ✓                  | ✓                  |
+| Dialog Rails <br/> (refuse unwanted topics)         | x          | x                  | ✓                  | ✓                  |
+| Moderation Rails <br/> (input/output self-checking) | x          | x                  | x                  | ✓                  |
 
 The results for each vulnerability category tested by Garak are summarized in the table below.
 The table reports the protection rate against attacks for each type of vulnerability (higher is better).