Deprecate Send Reassure Performance Tests to Graphite workflow

The workflow ran on every merge to main and pushed Reassure baseline
numbers to stats.expensify.com for Graphite ingestion. Perf regressions
are already caught by the Reassure Performance Tests workflow that runs
on every PR, and the Graphite dashboards fed by this job are not used,
so this is pure CI cost.

- Delete .github/workflows/sendReassurePerfData.yml
- Delete the getGraphiteString GH Action, which is only used here
- Drop the getGraphiteString entry from buildActions.sh

Made-with: Cursor

Author: mountiny