feat: update gapic-common for generated libraries to 1.4

[torreypayne]

gapic-common 1.4.0 requires grpc >= 1.83, the first grpc release that negotiates the X25519MLKEM768 post-quantum key exchange by default (googleapis/ruby-core-libraries#73).

Generated clients currently declare gapic-common "~> 1.3". That permits 1.4.0 but does not require it: a resolver can backtrack to 1.3.0 and its grpc "~> 1.66" constraint, silently landing on a classical-only transport. Raising the emitted floor to "~> 1.4" guarantees that every client version released from now on runs on a PQC-capable grpc.

Scope: this does not make PQC a hard requirement for applications. Bundler can still backtrack the client gem itself to an older release that allows a classical-only grpc. A hard guarantee is only possible at the application level, e.g. by requiring grpc ">= 1.83" in the app's own Gemfile.

Changes

• gem_presenter.rb: default gapic-common dependency ~> 1.3 → ~> 1.4.
• 13 goldens regenerated with toys gen; one line each.

Not changed: compute_small and compute_small_wrapper pin gapic-common: ">= 1.1|< 2.a" in their configs, which overrides the default by design. Production libraries that set ruby-cloud-extra-dependencies=gapic-common=… behave the same way and will need their own update.

Follows the precedent set by #1223 (feat: update gapic-common for generated libraries to 1.2).