Fix text color issue in CustomSlashMenu for dark mode (#9280)

fixes #9265 

#### Summary
The menu options appear in black color in dark mode, making text hard to
read because there is very little contrast between text and background.

#### Solution
Added `color: ${({ theme }) => theme.font.color.secondary};` to the
dropdown menu container, so the menu options inherit the correct text
color from their containers.

### Screenshots
![CleanShot 2024-12-30 at 09 37
26](https://github.com/user-attachments/assets/a709b785-75a4-408d-9517-d3cab2c1fee6)

packages/twenty-front/src/modules/ui/input/editor/components/CustomSlashMenu.tsx

@@ -23,6 +23,7 @@ const StyledContainer = styled.div`
 `;
 
 const StyledInnerContainer = styled.div`
+  color: ${({ theme }) => theme.font.color.secondary};
   height: 250px;
   width: 100%;
 `;