Skip dotnet 6.0 tests in release script (#329)

Pass through the language version, so we can skip the donet template
tests when running on dotnet 6.0. Our templates have been updated to use
8.0

Follow up to #320
which updated the PR workflow, but not the release workflow.

.github/workflows/release.yml

@@ -519,6 +519,7 @@ jobs:
           docker run \
             -e RUN_CONTAINER_TESTS=true \
             -e IMAGE_VARIANT=pulumi-debian-${{ matrix.sdk }} \
+            -e LANGUAGE_VERSION=${{ matrix.language_version }} \
             -e SDKS_TO_TEST=${SDKS_TO_TEST} \
             -e PULUMI_ACCESS_TOKEN=${PULUMI_ACCESS_TOKEN} \
             -e PULUMI_ORG=${PULUMI_ORG} \
@@ -729,6 +730,7 @@ jobs:
           docker run \
             -e RUN_CONTAINER_TESTS=true \
             -e IMAGE_VARIANT=pulumi-ubi-${{ matrix.sdk }} \
+            -e LANGUAGE_VERSION=${{ matrix.language_version }} \
             -e SDKS_TO_TEST=${SDKS_TO_TEST} \
             -e PULUMI_ACCESS_TOKEN=${PULUMI_ACCESS_TOKEN} \
             -e PULUMI_ORG=${PULUMI_ORG} \