feat(infra): upgrade postgresql SKU in test (#1257)

<!--- Provide a general summary of your changes in the Title above -->

## Description

<!--- Describe your changes in detail -->

<img width="1091" alt="image"
src="https://github.com/user-attachments/assets/6f3f9095-ccc7-4342-8f47-fdacb733f9be">

Seems like it's CPU that we are struggling with the most. Upgrading to
the next profile in the Burstable tier which has 2 cores. (B2s)

## Related Issue(s)

- #292 

## Verification

- [ ] **Your** code builds clean without any errors or warnings
- [ ] Manual testing done (required)
- [ ] Relevant automated test added (if you find this hard, leave it and
we'll help out)

## Documentation

- [ ] Documentation is updated (either in `docs`-directory, Altinnpedia
or a separate linked PR in
[altinn-studio-docs.](https://github.com/Altinn/altinn-studio-docs), if
applicable)


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

## Summary by CodeRabbit

- **New Features**
- Enhanced flexibility in PostgreSQL SKU selection with additional
options available.
- Updated default SKU from 'Standard_B1ms' to 'Standard_B2s' for
improved resource allocation.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.azure/infrastructure/test.bicepparam

@@ -30,7 +30,7 @@ param slackNotifierSku = {
   applicationServicePlanTier: 'Dynamic'
 }
 param postgresSku = {
-  name: 'Standard_B1ms'
+  name: 'Standard_B2s'
   tier: 'Burstable'
 }
 

.azure/modules/postgreSql/create.bicep

@@ -24,7 +24,7 @@ param tags object
 
 @export()
 type Sku = {
-  name: 'Standard_B1ms'
+  name: 'Standard_B1ms' | 'Standard_B2s' | 'Standard_B4ms' | 'Standard_B8ms' | 'Standard_B12ms' | 'Standard_B16ms' | 'Standard_B20ms'
   tier: 'Burstable' | 'GeneralPurpose' | 'MemoryOptimized'
 }