Update docs with permissions required for error tracking

See merge request gitlab-org/gitlab-ce!25208

(cherry picked from commit 1e5c83f2)

4202f259 Update docs with permissions for error tracking
df00f7c5 Add line to doc listing reqd Sentry token scopes
6d40af7c Apply suggestion to doc/user/project/operations/error_tracking.md
68d92af4 Apply suggestion to doc/user/project/operations/error_tracking.md
192e3ed4 Apply suggestion to doc/user/project/operations/error_tracking.md
d7e03aff Add Manage Error Tracking permission to table