Pulling different versions of xterm.js

[msujew]

I've noticed that we're pulling 2 different versions of xterm.js in our build. One in @theia/terminal:

theia/packages/terminal/package.json

Lines 14 to 16 in 69b8877

	"xterm": "^5.3.0",
	"xterm-addon-fit": "^0.8.0",
	"xterm-addon-search": "^0.13.0"

And in @theia/test:

theia/packages/test/package.json

Lines 11 to 12 in 69b8877

	"xterm": "^4.16.0",
	"xterm-addon-fit": "^0.5.0"

We should probably update the one from @theia/test to align with the one from @theia/terminal. Maybe even re-export it?

We likely forgot to bump the version in both packages due to the long review time on #12691.