fix MarkdownView, SwitchView, and Placement

[imanjra]

What changes are proposed in this pull request?

(Please fill in changes proposed in this fix)

How is this patch tested? If it is not, please explain why.

(Details)

Release Notes

Is this a user-facing change that should be mentioned in the release notes?

• No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release
  notes for FiftyOne users.

(Details in 1-2 sentences. You can just refer to another PR with a description
if this PR is part of a larger change.)

What areas of FiftyOne does this PR affect?

• App: FiftyOne application changes
• Build: Build and test infrastructure changes
• Core: Core fiftyone Python library changes
• Documentation: FiftyOne documentation changes
• Other

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (83c1ebc) 15.84% compared to head (7ef5819) 15.84%.
Report is 36 commits behind head on release/v0.22.0.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/v0.22.0    #3537   +/-   ##
================================================
  Coverage            15.84%   15.84%           
================================================
  Files                  593      593           
  Lines                72768    72767    -1     
  Branches               861      861           
================================================
  Hits                 11533    11533           
+ Misses               61235    61234    -1     

Flag	Coverage Δ
app	15.84% <0.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...e/src/plugins/SchemaIO/components/MarkdownView.tsx	0.00% <0.00%> (ø)
...ore/src/plugins/SchemaIO/components/SwitchView.tsx	0.00% <0.00%> (ø)
app/packages/operators/src/OperatorPlacements.tsx	0.00% <ø> (ø)

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[brimoor]

LGTM