Edited text is displayed as plaintext instead of markdown

[kieferrm]

Issue Type: Bug

1. Edit the description of a PR on the PR overview page. Use back-tick and empty lines to separate paragraphs
2. Save

Get this:

Note: When you reopen the editor, the presentation is correct.

Extension version: 2019.11.2342
VS Code version: Code - Insiders 1.41.0-insider (7cf4cca47aa025a590fc939af54932042302be63, 2019-12-02T05:26:29.458Z)
OS version: Darwin x64 18.7.0
Fetching remote diagnostics for 'ssh-remote+az-devbox' timed out.

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz (8 x 2500)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off surface_control: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	16.00GB (0.51GB free)
Process Argv	-psn_0_12958811
Screen Reader	no
VM	0%

Fetching remote diagnostics for 'ssh-remote+az-devbox' timed out.