Add rc4 PR to changelog

Signed-off-by: Stephen Curran <swcurran@gmail.com>

Author: swcurran

CHANGELOG.md

@@ -178,6 +178,7 @@ stuff needed for a growing codebase.
   - run_docker start - pass environment variables [\#1715](https://github.com/hyperledger/aries-cloudagent-python/pull/1715) ([shaangill025](https://github.com/shaangill025))
 
 - Release management pull requests
+  - Update changelog and version for 0.7.4-rc4 [\#1830](https://github.com/hyperledger/aries-cloudagent-python/pull/1830) ([swcurran](https://github.com/swcurran))
   - Changelog, version and ReadTheDocs updates for 0.7.4-rc3 release [\#1817](https://github.com/hyperledger/aries-cloudagent-python/pull/1817) ([swcurran](https://github.com/swcurran))
   - 0.7.4-rc2 update [\#1771](https://github.com/hyperledger/aries-cloudagent-python/pull/1771) ([swcurran](https://github.com/swcurran))
   - Some ReadTheDocs File updates [\#1770](https://github.com/hyperledger/aries-cloudagent-python/pull/1770) ([swcurran](https://github.com/swcurran))