Fix minor typo (#218)

Author: robberwick

_docs/concepts/client_library/real-time_executor/index.md

@@ -38,7 +38,7 @@ permalink: /docs/concepts/client_library/real-time_executor/
 
 Predictable execution under given real-time constraints is a crucial requirement for many robotic applications. While the service-based paradigm of ROS allows a fast integration of many different functionalities, it does not provide sufficient control over the execution management. For example, there are no mechanisms to enforce a certain execution order of callbacks within a node. Also the execution order of multiple nodes is essential for control applications in mobile robotics. Cause-effect-chains comprising of sensor acquisition, evaluation of data and actuation control should be mapped to ROS nodes executed in this order, however there are no explicit mechanisms to enforce it. Furthermore, when input data is collected in field tests, saved with ROS-bags and re-played, often results are different due to non-determinism of process scheduling.
 
-Manually setting up a particular execution order of subscribing and publishing topics in the callbacks or by tweaking the priorities of the corresponding Linux processes is always possible. However, this approach is error-prune, difficult to extend and requires an in-depth knowledge of the deplyed ROS 2 packages in the system.
+Manually setting up a particular execution order of subscribing and publishing topics in the callbacks or by tweaking the priorities of the corresponding Linux processes is always possible. However, this approach is error-prone, difficult to extend and requires an in-depth knowledge of the deplyed ROS 2 packages in the system.
 
 Therefore the goal of the Real-Time Executor is to support roboticists with practical and easy-to-use real-time mechanisms which provide solutions for:
 - Deterministic execution