feat(@schematics/angular): add migration to remove default Karma conf… #1792

Job	Run time
lint	2m 9s
build	14s
e2e_windows (windows-2025, 22, npm, 4)	29s
e2e_windows (windows-2025, 22, npm, 3)	34s
e2e_windows (windows-2025, 22, npm, 0)	44s
e2e_windows (windows-2025, 22, npm, 1)	34s
e2e_windows (windows-2025, 22, esbuild, 2)	32s
e2e_windows (windows-2025, 22, npm, 2)	34s
e2e_windows (windows-2025, 22, npm, 5)	32s
e2e_windows (windows-2025, 22, esbuild, 4)	35s
e2e_windows (windows-2025, 22, esbuild, 0)	36s
e2e_windows (windows-2025, 22, esbuild, 3)	33s
e2e_windows (windows-2025, 22, esbuild, 1)	31s
e2e_windows (windows-2025, 22, esbuild, 5)	39s
publish-snapshots	-1s
Browser Compatibility Tests	-1s
test	-1s
e2e-package-managers	0s
e2e	0s
e2e-snapshots	0s
	9m 13s

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