Remove command line flag which caused blurriness and missing pixels on Windows

[bsclifton]

This was originally added to fix #4517, #4518, and #4472... but is no longer needed (I confirmed all those situations work).

Fixes #6462
Fixes #6777
Fixes #6144
Fixes #3556
Fixes #2089

Auditors: @bridiver, @bbondy, @darkdh

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Verify there are no regressions

verify #4517 (Unable to select text on a page opened in a new tab following a link)

1. Open brianbondy.com
2. Click on Twitter image to open the twitter page in a new tab
3. Try selecting any text, not possible to select, text selection flickers when mouse is dragged across the text

verify #4518 (Link hover indicators flicker when moving the cursor across links on tabs opened from links)

1. Set DPI to > 100 (125%, 200%)
2. Visit https://github.com/brave/browser-laptop/issues
3. Move mouse over various links. You should not see flickering in other (unrelated) divs

verify #4472 (Mouse scrolling wheel issues)

1. go to http://jsbin.com/gesayaqoho/edit?html,output
2. click link shown in UI on right (has target=_blank)
3. notice you can scroll just fine

Test plan

1. Set DPI to 125%, 150%, 175% by right clicking desktop and picking display settings
2. Launch Brave
3. Visit about:autofill
4. Click "Add Address" to bring up the modal
5. Verify there are no missing pixels, as seen in Missing pixels at 125% - 175% DPI on Windows (and also blurriness) #6462
6. Close the modal and visit Brave.com
7. Hit Ctrl + D to bookmark page
8. Notice bookmark hanger is not blurry

[bbondy]

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[darkdh]

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