make widget card stack padding and title size consistent

[rebron]

Description

Widget card stack padding and title sizes need to be made consistent for all widgets in the stack

Design:

Brave version (brave://version info)

Brave	1.9.21 Chromium: 81.0.4044.92 (Official Build) nightly (64-bit)
Revision	32921c79b6f01a0fb2deef0e1d45b42f96581051-refs/branch-heads/4044@{#883}
OS	macOS Version 10.15.5 (Build 19F53f)

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the dev channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

[srirambv]

Verification passed on

Brave	1.9.37 Chromium: 81.0.4044.113 (Official Build) nightly (64-bit)
Revision	cf9d66371ea608e227eed56ccba3abc2701bd23d-refs/branch-heads/4044@{#936}
OS	Windows 10 OS Version 1909 (Build 18363.778)

• Verified widget title uses 18px Poppins font
  
• Verified cards use rounded corners
  
• Logged issue for gap between card stack Gap behind card stack  #9385

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Verification passed on

Brave	1.9.37 Chromium: 81.0.4044.113 (Official Build) nightly (64-bit)
Revision	cf9d66371ea608e227eed56ccba3abc2701bd23d-refs/branch-heads/4044@{#936}
OS	Linux

• Verified widget title uses 18px Poppins font
• Verified cards use rounded corners

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Verification passed on

Brave	1.9.37 Chromium: 81.0.4044.113 (Official Build) nightly (64-bit)
Revision	cf9d66371ea608e227eed56ccba3abc2701bd23d-refs/branch-heads/4044@{#936}
OS	macOS Version 10.15.4 (Build 19E287)

• Verified widget title uses 18px Poppins font
• Verified cards use rounded corners