Bump ccxt from 1.60.11 to 1.60.68

Bumps [ccxt](https://github.com/ccxt/ccxt) from 1.60.11 to 1.60.68.
- [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/1.60.11...1.60.68)

---
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

@@ -2,7 +2,7 @@ numpy==1.21.3
 pandas==1.3.4
 pandas-ta==0.3.14b
 
-ccxt==1.60.11
+ccxt==1.60.68
 # Pin cryptography for now due to rust build errors with piwheels
 cryptography==35.0.0
 aiohttp==3.7.4.post0