Dockerfile: Add missing 'rm -rf /tmp/coreboot-24.08'

We had missed removing the coreboot directory once done, fix this.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/docker/Dockerfile b/tools/docker/Dockerfile
index 85d6784..5699123 100644
--- a/tools/docker/Dockerfile
+++ b/tools/docker/Dockerfile
@@ -296,7 +296,8 @@
     make olddefconfig && \
     make -j $(nproc) && \
     sudo mkdir /opt/coreboot && \
-    sudo cp build/coreboot.rom build/cbfstool /opt/coreboot/
+    sudo cp build/coreboot.rom build/cbfstool /opt/coreboot/ && \
+    rm -rf /tmp/coreboot-24.08
 
 # Create our user/group
 RUN echo uboot ALL=NOPASSWD: ALL > /etc/sudoers.d/uboot