Dockerfile: healthcheck dont use sh

- interpreter already set in the scripts not need to use /bin/sh -c
Signed-off-by: Lakshya Singh <lakshay.singh1108@gmail.com>

lightningd/Dockerfile

@@ -159,7 +159,7 @@ RUN pip3 install \
       packaging
 
 HEALTHCHECK --interval=5s --timeout=10s --start-period=5s \
-    CMD ["/bin/sh", "-c", "/healthcheck.sh"]
+    CMD ["/healthcheck.sh"]
 
 ENTRYPOINT ["/entrypoint.sh"]
 CMD ["lightningd"]