Remove box around matchBrackets

[vchouhan]

• VSCode Version: Version 1.10.2 (1.10.2)
• OS Version: Mac OS 10.4

Steps to Reproduce:

1. Enable matchBrackets to true
2. Cursor to be 'line-thin'
3. Add the following syntax {} and move the cursor in between the curly braces, see the cursor line and the boxes borders overlap, it's difficult to see the cursor position while coding.

[fakewaffle]

Is there a way to style the matching brackets? I would much prefer to just bold them instead of having a box. It's very hard to see the cursor with line or line-thin when there is a box.

[fakewaffle]

Probably the same as #19534.

[alexdima]

Let's track in #19534