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>

bitcoind/Dockerfile

@@ -136,6 +136,6 @@ ENTRYPOINT ["/entrypoint.sh"]
 RUN bitcoind -version | grep "Bitcoin Core version v${BITCOIN_VERSION}"
 
 HEALTHCHECK --interval=10s --timeout=20s --start-period=30s \
-  CMD ["/bin/sh", "-c", "/healthcheck.sh"]
+  CMD ["/healthcheck.sh"]
 
 CMD ["bitcoind"]