docs: remove curly brace from readme

The curly brace breaks the Docusaurus complication.

Signed-off-by: Michael Beemer <beeme1mr@users.noreply.github.com>

Author: beeme1mr

README.md

@@ -613,8 +613,8 @@ Below are the metrics extracted by this hook and dimensions they carry:
 
 | Metric key                             | Description                     | Unit         | Dimensions                    |
 | -------------------------------------- | ------------------------------- | ------------ | ----------------------------- |
-| feature_flag.evaluation_requests_total | Number of evaluation requests   | {request}    | key, provider name            |
-| feature_flag.evaluation_success_total  | Flag evaluation successes       | {impression} | key, provider name, reason    |
+| feature_flag.evaluation_requests_total | Number of evaluation requests   | request      | key, provider name            |
+| feature_flag.evaluation_success_total  | Flag evaluation successes       | impression   | key, provider name, reason    |
 | feature_flag.evaluation_error_total    | Flag evaluation errors          | 1            | key, provider name, exception |
 | feature_flag.evaluation_active_count   | Active flag evaluations counter | 1            | key, provider name            |