Update install-ubuntu.md
Update install-ubuntu.md

Fixed small grammatical error (sending this doc change through GH to demonstrate how this change process looks for a completely external contributor, see also https://github.com/bazelbuild/bazel/pull/2784)

Closes #2786.

PiperOrigin-RevId: 156342450

aehlig/bazel,spxtr/bazel,davidzchen/bazel,aehlig/bazel,dslomov/bazel-windows,werkt/bazel,spxtr/bazel,ButterflyNetwork/bazel,spxtr/bazel,bazelbuild/bazel,davidzchen/bazel,twitter-forks/bazel,cushon/bazel,akira-baruah/bazel,dropbox/bazel,damienmg/bazel,variac/bazel,dslomov/bazel,juhalindfors/bazel-patches,dslomov/bazel,ulfjack/bazel,twitter-forks/bazel,cushon/bazel,dropbox/bazel,variac/bazel,perezd/bazel,snnn/bazel,bazelbuild/bazel,twitter-forks/bazel,akira-baruah/bazel,dropbox/bazel,katre/bazel,snnn/bazel,meteorcloudy/bazel,safarmer/bazel,dropbox/bazel,meteorcloudy/bazel,katre/bazel,ButterflyNetwork/bazel,werkt/bazel,akira-baruah/bazel,juhalindfors/bazel-patches,dslomov/bazel-windows,katre/bazel,meteorcloudy/bazel,snnn/bazel,ButterflyNetwork/bazel,safarmer/bazel,aehlig/bazel,dslomov/bazel,werkt/bazel,ButterflyNetwork/bazel,variac/bazel,dslomov/bazel,ulfjack/bazel,meteorcloudy/bazel,dropbox/bazel,cushon/bazel,damienmg/bazel,dslomov/bazel,werkt/bazel,meteorcloudy/bazel,twitter-forks/bazel,damienmg/bazel,akira-baruah/bazel,ulfjack/bazel,variac/bazel,meteorcloudy/bazel,snnn/bazel,katre/bazel,katre/bazel,ButterflyNetwork/bazel,perezd/bazel,snnn/bazel,perezd/bazel,spxtr/bazel,safarmer/bazel,perezd/bazel,variac/bazel,bazelbuild/bazel,perezd/bazel,cushon/bazel,bazelbuild/bazel,bazelbuild/bazel,dslomov/bazel-windows,davidzchen/bazel,damienmg/bazel,meteorcloudy/bazel,twitter-forks/bazel,cushon/bazel,aehlig/bazel,bazelbuild/bazel,davidzchen/bazel,davidzchen/bazel,twitter-forks/bazel,davidzchen/bazel,cushon/bazel,juhalindfors/bazel-patches,snnn/bazel,dslomov/bazel-windows,dropbox/bazel,damienmg/bazel,aehlig/bazel,perezd/bazel,damienmg/bazel,damienmg/bazel,ButterflyNetwork/bazel,variac/bazel,juhalindfors/bazel-patches,variac/bazel,dslomov/bazel,spxtr/bazel,ulfjack/bazel,ulfjack/bazel,akira-baruah/bazel,dslomov/bazel-windows,katre/bazel,davidzchen/bazel,ulfjack/bazel,werkt/bazel,juhalindfors/bazel-patches,spxtr/bazel,aehlig/bazel,snnn/bazel,juhalindfors/bazel-patches,aehlig/bazel,safarmer/bazel,safarmer/bazel,dslomov/bazel-windows,perezd/bazel,twitter-forks/bazel,spxtr/bazel,dslomov/bazel,juhalindfors/bazel-patches,safarmer/bazel,werkt/bazel,akira-baruah/bazel,ulfjack/bazel