fix: rename rule no-empty-enum-servers to no-server-variables-empty-enum (#813)

* fix: rename rule no-empty-enum-servers to no-server-variables-empty-enum
- fix no-server-example.com docs

* chore: fix snapshots

Co-authored-by: Andrew Tatomyr <andrew.tatomyr@redocly.com>

__tests__/lint/no-server-variables-empty-enum-errror/snapshot.js

@@ -0,0 +1,40 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`E2E lint no-server-variables-empty-enum-errror 1`] = `
+
+validating /openapi.yaml...
+[1] openapi.yaml:5:1 at #/servers
+
+Server variable with \`enum\` must be a non-empty array.
+
+3 |   title: Example OpenAPI 3 definition. Valid.
+4 |   version: 1.0
+5 | servers:
+  | ^^^^^^^
+6 |   - url: https://example.com/user/{id}/place/{placeId}
+7 |     variables:
+
+Error was generated by the no-server-variables-empty-enum rule.
+
+
+[2] openapi.yaml:5:1 at #/servers
+
+Server variable define \`enum\` and \`default\`. \`enum\` must include default value
+
+3 |   title: Example OpenAPI 3 definition. Valid.
+4 |   version: 1.0
+5 | servers:
+  | ^^^^^^^
+6 |   - url: https://example.com/user/{id}/place/{placeId}
+7 |     variables:
+
+Error was generated by the no-server-variables-empty-enum rule.
+
+
+/openapi.yaml: validated in <test>ms
+
+❌ Validation failed with 2 errors.
+run \`openapi lint --generate-ignore-file\` to add all problems to the ignore file.
+
+
+`;