test: correct default runs to 1<<32 in aggregator_test

[zeevick10]

Description:

• Summary: Replace incorrect XOR expression (2 ^ 32) with the intended exponent-equivalent bit shift (1 << 32) for the default runs value in aggregator_test.
• Rationale: 2 ^ 32 in Go is bitwise XOR (resulting in 34), not exponentiation. This was misleading and could affect future changes if bounds are adjusted.
• Changes:
  • Set runs default to 1 << 32 in daprovider/das/aggregator_test.go.