Bump ccxt from 1.51.40 to 1.51.77

Bumps [ccxt](https://github.com/ccxt/ccxt) from 1.51.40 to 1.51.77.
- [Release notes](https://github.com/ccxt/ccxt/releases)
- [Changelog](https://github.com/ccxt/ccxt/blob/master/exchanges.cfg)
- [Commits](https://github.com/ccxt/ccxt/compare/1.51.40...1.51.77)

---
updated-dependencies:
- dependency-name: ccxt
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,7 +1,7 @@
 numpy==1.20.3
 pandas==1.2.4
 
-ccxt==1.51.40
+ccxt==1.51.77
 # Pin cryptography for now due to rust build errors with piwheels
 cryptography==3.4.7
 aiohttp==3.7.4.post0