Terminal Output incorrectly rendered for IEx help

[RyanHirsch]

When using Elixir's Interactive Shell the help headings for functions is incorrectly formatted. It should be a yellow bar with black letters to indicate the name of the function, instead it is a shortened, non-contiguous bar with no text.

• VSCode Version: Code - Insiders 1.17.0-insider (f7962f0, 2017-09-20T05:10:59.524Z)
• OS Version: Darwin x64 16.7.0
• Extensions:

Extension	Author (truncated)	Version
vscode-markdownlint	Dav	0.10.1
EditorConfig	Edi	0.10.1
material-icon-theme	PKi	2.2.1
vscode-docker	Pet	0.0.18
code-settings-sync	Sha	2.8.3
better-toml	bun	0.3.1
vscode-eslint	dba	1.3.2
vscode-babel-coloring	dza	0.0.4
gitlens	eam	5.2.0
rest-client	hum	0.15.2
terraform	mau	0.0.18
vscode-elixir	mjm	1.0.0
prettify-json	moh	0.0.3
cpptools	ms-	0.12.4
elm	sbr	0.15.0
vscode-nginx	sha	0.4.1
vim	vsc	0.10.1

(3 theme extensions excluded)

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Steps to Reproduce:

1. Open terminal
2. Launch iex
3. Run h String.split/1

Reproduces without extensions: Yes

[Tyriar]

Duplicate #35151