Remove confirm button from changing theme option in onboarding

[srirambv]

Description

Remove confirm button from changing theme option in onboarding

Actual result:

Expected result:

No confirm button required as the drop-down makes the visual change instantly

cc: @simonhong @rebron @rossmoody

[kjozwiak]

Also mentioned via #1548 (comment) where we had a discussion regarding removing both of the Confirm buttons for both Search and Themes.

Agreed that the confirm button seems a but redundant for theme selection. However, @rossmoody made some good points via #1548 (comment). However, might be more applicable to the Confirm button for Search.

[srirambv]

I feel instead of having the confirm button, we can just add a text label that says New search engine set if user changes the default from dropdown. The button placement looks odd to me. Adding the text makes visual confirmation as well and avoids awkward button placement as well. Just a thought but will leave decision upto the design team

[kjozwiak]

CCing @rossmoody to update the above with a possible new implementation discussed on Slack.

[rossmoody]

I think the direction of this one can stay as-is. Removing the confirm button for this panel is non-detrimental and users can use the next button.

[GeetaSarvadnya]

Verification passed on

Brave	0.69.128 Chromium: 77.0.3865.75 (Official Build) (64-bit)
Revision	201e747d032611c5f2785cae06e894cf85be7f8a-refs/branch-heads/3865@{#776}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the test plan from Theme fix brave-core#3088
• Verified the STR from the description

Verification passed on

Brave	0.69.128 Chromium: 77.0.3865.75 (Official Build) (64-bit)
Revision	201e747d032611c5f2785cae06e894cf85be7f8a-refs/branch-heads/3865@{#776}
OS	Ubuntu 18.04 LTS

• Verified the test plan from Theme fix brave-core#3088
• Verified the STR from the description

Verification PASSED on macOS 10.14.6 x64 using the following build:

Brave	0.69.129 Chromium: 77.0.3865.90 (Official Build) (64-bit)
Revision	58c425ba843df2918d9d4b409331972646c393dd-refs/branch-heads/3865@{#830}
OS	macOS Version 10.14.6 (Build 18G95)