Tiny UI issue - non-sentence case text in Infrastructure UI page

[Titch990]

Kibana version: 7.3.0

Elasticsearch version: 7.3.0

Server OS version: MacOS

Browser version: Safari

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.): 7.x.x-BC build from here https://github.com/elastic/observability-dev/blob/master/docs/observability-clusters.md

Describe the bug:
In the infrastructure Inventory page, there are several text strings that are not in sentence case. @gchaps and I think they probably should be.

This affects:

• Map View (should be "Map view")
• Table View (should be "Table view")
• Most of the items listed in the Metric dropdown, for example "CPU Usage" to "CPU usage", "Memory Usage" to "Memory usage"
• The text "Group By" (should be "Group by") and most of the text in the dropdown also needs to be changed, for example "Custom field" to "Custom field")

"Metrics Explorer" is OK as that's been agreed as an actual name rather than UI text.

Steps to reproduce:

1. Open Kibana and select the Infrastructure app.

Expected behavior: As above.

[elasticmachine]

Pinging @elastic/infra-logs-ui