fix(docs): correct topics values to align with expected enums (#45140)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

## What kind of change does this PR introduce?

Docs update to correct frontmatter values in topics array to align with
expected enums. In this case "REST-API" is not one of the excepted enum
values for the topics array.

Excepted values:

```
topics: z.array(
      z.enum([
        'ai',
        'auth',
        'branching',
        'cli',
        'database',
        'functions',
        'platform',
        'realtime',
        'self-hosting',
        'storage',
        'studio',
        'supavisor',
        'terraform',
      ])
    ),
```

Added keywords for the additional value.

## What is the current behavior?

These troubleshooting guides are not rendered in front-facing docs
despite being available in the content/troubleshooting directory due to
error validating troubleshooting metadata

## What is the new behavior?

These troubleshooting guides are now rendered.



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Documentation**
* Updated frontmatter in troubleshooting guides: removed "rest-api" from
topics and added a "REST API" keyword to improve content organization
and searchability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Chandana Anumula <129955975+canumula@users.noreply.github.com>

apps/docs/content/troubleshooting/postgrest-not-recognizing-objects-in-schema.mdx

@@ -2,10 +2,9 @@
 title = "PostgREST not recognizing the objects(tables/functions/views) in a schema even after adding it to the exposed schemas"
 topics = [
 "database",
-"rest-api",
 "platform"
 ]
-keywords = []
+keywords = ["REST API"]
 ---
 
 PostgREST is returning errors by not recognizing the objects(tables/functions/views) in a schema and logging errors similar to:

apps/docs/content/troubleshooting/schema-pg_pgrst_no_exposed_schemas-does-not-exist.mdx

@@ -2,9 +2,9 @@
 title = "schema \"pg_pgrst_no_exposed_schemas\" does not exist"
 topics = [
 "database",
-"rest-api",
 "platform"
 ]
+keywords = ["REST API"]
 [[errors]]
 message = "schema pg_pgrst_no_exposed_schemas does not exist"
 ---