fix: Correct theme value for Snap UI footer buttons

[FrederikBolding]

Description

The Snap UI footer buttons use the DS button which forces light theme, this does not work for the colors used in the Snap buttons, therefore we revert back to using the actually selected theme.

Related issues

Fixes: #29388

Screenshots/Recordings

Before

After

[metamaskbot]

Builds ready [385b244]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 10, 11, 12, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • offscreen: 0
  • ui: 0, 1, 10, 11, 12, 13, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (1897 ± 57 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	569	2214	1825	314	151
		domContentLoaded	1666	2147	1863	117	56
		load	1683	2199	1897	119	57
		domInteractive	29	127	56	28	14
		backgroundConnect	10	95	33	25	12
		firstReactRender	18	103	58	32	15
		getState	6	88	41	32	15
		initialActions	0	1	0	0	0
		loadScripts	1238	1642	1394	97	46
		setupStore	7	58	16	16	7
		uiStartup	1983	2745	2285	218	104