package/bitcoin: security bump to version 0.20.1

package/bitcoin: security bump to version 0.20.1

- openssl is not a dependency since version 0.20.0 and
  https://github.com/bitcoin/bitcoin/commit/8983ee3e6dd8ab658bd2caf97c326cc53ea50818
- boost chrono is not needed since version 0.20.0 and
  https://github.com/bitcoin/bitcoin/commit/bd37f2bc26158f85ef1ab73b9ca1fc0da8ea562a
- Update hash of COPYING (update in year:
  https://github.com/bitcoin/bitcoin/commit/8dc9aa90c3c7990dd5b491937ddc0e39bc929d1c)
- Update indentation in hash file (two spaces)
- Tag as a security bump as having an up to date bitcoin is important:
  https://patchwork.ozlabs.org/project/buildroot/patch/20200202085526.35742-1-james.hilliard1@gmail.com

https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.20.1.md
https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.20.0.md
https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.19.1.md

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>