Terminal warnings when attempting to run webpack dev server

[turt2live]

2023-01-12 13:22:44.884 [element-js]
2023-01-12 13:22:44.884 [element-js] WARNING in ../matrix-react-sdk/res/themes/light/css/light.pcss (./node_modules/css-loader/dist/cjs.js??ref--8-1!./node_modules/postcss-loader/src??postcss!../matrix-react-sdk/res/themes/light/css/light.pcss)
2023-01-12 13:22:44.884 [element-js] Module Warning (from ./node_modules/postcss-loader/src/index.js):
2023-01-12 13:22:44.884 [element-js] Warning
2023-01-12 13:22:44.884 [element-js]
2023-01-12 13:22:44.884 [element-js] (1301:5) Replace fill-available to stretch, because spec had been changed
2023-01-12 13:22:44.884 [element-js]
2023-01-12 13:22:44.884 [element-js] WARNING in ../matrix-react-sdk/res/themes/dark/css/dark.pcss (./node_modules/css-loader/dist/cjs.js??ref--8-1!./node_modules/postcss-loader/src??postcss!../matrix-react-sdk/res/themes/dark/css/dark.pcss)
2023-01-12 13:22:44.884 [element-js] Module Warning (from ./node_modules/postcss-loader/src/index.js):
2023-01-12 13:22:44.884 [element-js] Warning
2023-01-12 13:22:44.884 [element-js]
2023-01-12 13:22:44.884 [element-js] (1301:5) Replace fill-available to stretch, because spec had been changed
2023-01-12 13:22:44.885 [element-js] i ｢wdm｣: Compiled with warnings.

[t3chguy]

Related #23597

[t3chguy]

@justjanne looks like this was introduced in one of your changes, could you take this on please?