Docs: monitoring, streaming programming guide

Fix several awkward wordings and grammatical issues in the following
documents:

*   docs/monitoring.md

*   docs/streaming-programming-guide.md

Author: kballou <kballou@devnulllabs.io>

Closes #1662 from kennyballou/grammar_fixes and squashes the following commits:

e1b8ad6 [kballou] Docs: monitoring, streaming programming guide

(cherry picked from commit cc820502fb08f71b03237103153c34487b2600b4)
Signed-off-by: Josh Rosen <joshrosen@apache.org>