ci(buildkit): remove regex skipping tests with digest inconsistency

Skipping digest-related tests is no longer necessary after https://github.com/containerd/containerd/commit/40658316526ee5e0ec91d110e5999abb0b9a5407

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>
Signed-off-by: Bjorn Neergaard <bjorn.neergaard@docker.com>

.github/workflows/buildkit.yml

@@ -124,6 +124,5 @@ jobs:
           TEST_DOCKERD: "1"
           TEST_DOCKERD_BINARY: "./build/moby/dockerd"
           TESTPKGS: "./${{ matrix.pkg }}"
-          # Skip buildkit tests checking the digest (see https://github.com/moby/buildkit/pull/3736)
-          TESTFLAGS: "-v --parallel=1 --timeout=30m --run=/^Test([^R]|.[^e]|..[^p]|...[^r]|....[^o]|.....[^S])/worker=${{ matrix.worker }}$"
+          TESTFLAGS: "-v --parallel=1 --timeout=30m --run=//worker=${{ matrix.worker }}$"
         working-directory: buildkit