Make all 4 corners of tip panel rounded on all platforms

[zenparsing]

On MacOS, all four corners of the panel are rendered with the same radius, even when different values are specified for each corner (likely due to an upstream bug). In order to normalize across platforms and avoid issues, we should temporarily make all corners rounded on all desktop platforms.

[LaurenWags]

@brave/qa-team when testing on Windows, please test this on both Windows 10 and Windows 11. Do not add QA Pass-Win64 label until both platforms are verified, thanks!

[kjozwiak]

The above requires 1.52.110 or higher for 1.52.x verification 👍

[LaurenWags]

Verified with

Brave | 1.52.110 Chromium: 114.0.5735.35 (Official Build) (x86_64)
-- | --
Revision | 2295354895fa3652ae47b651481831484f16d1ff-refs/branch-heads/5735@{#713}
OS | macOS Version 13.4 (Build 22F66)

Confirmed all 4 corners of contribution (tip) banner are rounded for various tip banners.
Confirmed on both Dark and Light themes.

Dark	Light

[MadhaviSeelam]

Verification PASSED using

Brave | 1.52.110 Chromium: 114.0.5735.35 (Official Build) (64-bit)
-- | --
Revision | 2295354895fa3652ae47b651481831484f16d1ff-refs/branch-heads/5735@{#713}
OS | Windows 11 Version 22H2 (Build 22621.1702)

• Confirmed all 4 corners of contribution (tip) banner are rounded for various tip banners.
• Confirmed on both Dark and Light themes.

Dark	Light

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.52.112 Chromium: 114.0.5735.35 (Official Build) (64-bit)
-- | --
Revision | 2295354895fa3652ae47b651481831484f16d1ff-refs/branch-heads/5735@{#713}
OS | Windows 10 Version 22H2 (Build 19045.2965)

• Confirmed all 4 corners of contribution (tip) banner are rounded for various tip banners.
• Confirmed on both Dark and Light themes.

Dark	Light

[btlechowski]

Verification passed on

Brave	1.52.112 Chromium: 114.0.5735.35 (Official Build) (64-bit)
Revision	2295354895fa3652ae47b651481831484f16d1ff-refs/branch-heads/5735@{#713}
OS	Ubuntu 18.04 LTS

• Confirmed all 4 corners of contribution (tip) banner are rounded for various tip banners.
• Confirmed on both Dark and Light themes.

Light:

Dark: