fix(integrations): delete gemini_test.go after rename to prompts_test.go

The previous commit added prompts_test.go but did not stage the deletion
of gemini_test.go, leaving both files tracked by git and causing
duplicate function declaration errors in CI.

Relates to #68

Signed-off-by: Kavirubc <hapuarachchikaviru@gmail.com>

Author: Kavirubc