Update ChatHistoryService unit tests to cover a new storageType

[SDaniV]

Description

Update unit test for ChatHistoryService

Closes #268

What change does this PR introduce?

Please select the relevant option(s).

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to docs/code comments)

What is the proposed approach?

The proposed approach adds a new parameter storageType: "SESSION_STORAGE" to most of the unit tests inside ChatHistoryService.test.ts file to cover both storage types without duplicating the test blocks.

Screenshots:

Checklist:

• The commit message follows our adopted guidelines
• Testing has been done for the change(s) added (for bug fixes/features)
• Relevant comments/docs have been added/updated (for bug fixes/features)

[tjtanjin]

LGTM!