No background color and no bold text in diff pane

**Describe the bug**
I am not seeing background color or bold text in the diff panel. I recently upgraded from 0.25.1 to 0.28.1. In 0.25.1 I was not seeing this either. In 0.28.1, with a background color set, I was seeing blinking text. It also does not seem to be utilizing reverse coloring either if I try that. I'm using `diff-so-fancy`.

I find it interesting that other sections of lazygit will show bold, reverse, and background color (like the menus for instance) but the diff pane won't. Perhaps there's some clue there? 🤔

**To Reproduce**
Steps to reproduce the behavior:
1. Use Terminal.app on macOS
2. Open lazygit after having made a partial change to a line of code
3. View that file in lazygit

**Expected behavior**
All configurations of text style and coloring should be supported (or at least bold weight and background colors)

**Screenshots**
With this git config:
```
[color]
ui = true
[color "diff-highlight"]
oldNormal = red bold
oldHighlight = red bold 52
newNormal = green bold
newHighlight = green bold 22
[color "diff"]
meta = 11
frag = magenta bold
commit = yellow bold
old = red bold
new = green bold
whitespace = red reverse
```

I see this in `git diff`

and this in `lazygit`

----

With this git config
```
[color]
ui = true
[color "diff-highlight"]
oldNormal = red
oldHighlight = magenta bold
newNormal = green bold
newHighlight = green bold 22
[color "diff"]
meta = 11
frag = magenta bold
commit = yellow bold
old = red
new = green bold
whitespace = red reverse
```

I see this in `git diff`

and this in `lazygit`

**Desktop (please complete the following information):**
- OS: macOS 11.3
- Lazygit Version: 0.28.1
- The last commit ID: `9190e9beac90d80e854a726134b12e15d239df45` (according to `lazygit --version`)

**Additional context**
Add any other context about the problem here.