fix(aws-lambda): link GnuTLS dynamically in the arm64 ffmpeg build

With --static pkg-config flags, gnutls.pc names a libgmp.a from its own RPM build
tree and configure rejected GnuTLS. The codec libraries exist only as static
archives, so they still link statically. The recipe moves to image/, which will
also hold the video function image stage.

.github/workflows/lambda-ffmpeg.yml

@@ -8,7 +8,7 @@ permissions:
 on:
   pull_request:
     paths:
-      - "packages/aws-lambda/ffmpeg/**"
+      - "packages/aws-lambda/image/**"
       - ".github/workflows/lambda-ffmpeg.yml"
   workflow_dispatch:
 
@@ -29,7 +29,7 @@ jobs:
       - name: Build and check
         run: >-
           docker buildx build --progress=plain --platform linux/arm64 --target artifact
-          --output type=local,dest=out packages/aws-lambda/ffmpeg
+          --output type=local,dest=out packages/aws-lambda/image
       - run: cat out/hf-media-check.txt && sha256sum out/*.tar.gz
       - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with: