Update README.md (#275)

Signed-off-by: joethechicken <[email protected]>

README.md

@@ -50,7 +50,7 @@ The validator registration process consists of the following steps:
 
 ### Exit signatures rotation
 
-Exit signatures from the previous section can become invalid if the oracles set changes. For example, if oracle's
+Exit signatures from the previous section can become invalid if the oracles' set changes. For example, if oracles'
 private key gets compromised, the DAO will have to propose an update of the oracles set that will trigger exit signature
 rotation.
 The operator periodically checks active validators of the Vault and if some exit signatures become outdated, the