ci: Remove saucelabs

[rschristian]

Let me know if anyone is opposed to this, but it's been failing for the last 10 months straight, with 4 working commits, then another 5 months of failures which is where the actions history runs out.

Looks like karma-sauce-launcher has been abandoned w/ no changes in the last 2 years, and is 4 majors behind the current saucelabs version. Per NPM, the karma launcher down to half the downloads per week compared to last year, so I'm guessing everyone else is bailing off it too.

[github-actions]

Size Change: 0 B

Total Size: 62.1 kB

ℹ️ View Unchanged

Filename	Size
compat/dist/compat.js	4.13 kB
compat/dist/compat.module.js	4.05 kB
compat/dist/compat.umd.js	4.19 kB
debug/dist/debug.js	3.82 kB
debug/dist/debug.module.js	3.83 kB
debug/dist/debug.umd.js	3.9 kB
devtools/dist/devtools.js	260 B
devtools/dist/devtools.module.js	274 B
devtools/dist/devtools.umd.js	346 B
dist/preact.js	4.67 kB
dist/preact.min.js	4.69 kB
dist/preact.min.module.js	4.69 kB
dist/preact.min.umd.js	4.72 kB
dist/preact.module.js	4.68 kB
dist/preact.umd.js	4.73 kB
hooks/dist/hooks.js	1.53 kB
hooks/dist/hooks.module.js	1.56 kB
hooks/dist/hooks.umd.js	1.6 kB
jsx-runtime/dist/jsxRuntime.js	976 B
jsx-runtime/dist/jsxRuntime.module.js	949 B
jsx-runtime/dist/jsxRuntime.umd.js	1.05 kB
test-utils/dist/testUtils.js	451 B
test-utils/dist/testUtils.module.js	456 B
test-utils/dist/testUtils.umd.js	536 B

_{compressed-size-action}

[coveralls]

coverage: 99.488%. remained the same
when pulling 61f02fe on ci/saucelabs
into c9846f1 on main.

[rschristian]

We rely on core-js in our polyfill tests:

preact/test/polyfills.js

Line 2 in c9846f1

import 'core-js/es/map';

Undeclared dep, hence the additon here.