docs: applies wording suggested in #2154

[actualben]

What I did I applied a wording fix to docs/aci-container-features.md suggested in #2154, wherein the sentence:

A single container is executed in its own ACI container group, that will container only one container.

becomes:

A single container is executed in its own ACI container group, which will contain a single container.

Related issue

closes #2154