Bump client to 2.0.0-internal.1.4.0 (minor bump)

We are skipping 1.3.0, and 1.4.0 is being cut from the 1.2 release
branch.

The reason is that our former version numbers for pre-release and dev
builds were valid according to the semver ranges we provided to
partners, which means that they can inadvertently pick up a pre-release
build like 2.0.0-internal.1.3.0.56745 when they only intend to pick up
"released" Fluid internal versions.

Version series 1.0-1.3 (of 2.0) are thus "poisoned," so this bump along
with https://github.com/microsoft/FluidFramework/pull/12315 will push us
past the poisoned versions.