plugins: pin buildx to v0.3.1

Signed-off-by: Tibor Vass <tibor@docker.com>
(cherry picked from commit 41dfc51)
Signed-off-by: Tibor Vass <tibor@docker.com>
Upstream-commit: 46178072a3b6a63c6ab5f41eba912fb5023e7410
Component: packaging

Author: Tibor Vass

components/packaging/plugins/buildx.installer

@@ -6,7 +6,7 @@ source "$(dirname "$0")/.common"
 PKG=github.com/docker/buildx
 GOPATH=$(go env GOPATH)
 REPO=https://${PKG}.git
-: "${BUILDX_COMMIT=v0.3.0}"
+: "${BUILDX_COMMIT=v0.3.1}"
 DEST=${GOPATH}/src/${PKG}
 
 build() {