Notebook: no dirty state when outputs are updated

[rebornix]

Issue Type: Bug

When outputs of a cell are changed, the document doesn't become dirty.

VS Code version: Code - Insiders 1.44.0-insider (d7d1147, 2020-03-31T08:22:34.682Z)
OS version: Darwin x64 19.2.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz (16 x 2400)
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_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	32.00GB (3.78GB free)
Process Argv	-psn_0_2495073
Screen Reader	no
VM	0%

Extensions (16)

Extension	Author (truncated)	Version
comment-tagged-templates	bie	0.3.0
github-markdown-preview	bie	0.0.2
markdown-emoji	bie	0.0.9
markdown-preview-github-styles	bie	0.1.6
gitlens	eam	10.2.1
vscode-pull-request-github-insiders	Git	2020.3.35461
vscode-language-pack-zh-hans	MS-	1.44.0
remote-ssh-edit-nightly	ms-	2020.3.44100
remote-ssh-nightly	ms-	2020.3.44100
js-debug-nightly	ms-	2020.3.1617
vscode-github-issue-notebooks	ms-	0.0.3
vsliveshare	ms-	1.0.1891
debugger-for-chrome	msj	4.12.6
kuskus-extensions-pack	ros	1.0.1
kuskus-kusto-language-server	ros	1.0.1
kuskus-kusto-syntax-highlighting	ros	1.1.8

(4 theme extensions excluded)