Use go.uber.org/multierr instead of github.com/hashicorp/go-multierror

[k1LoW]

Switch now because go.uber.org/multierr has been maintained more recently.

[github-actions]

Code Metrics Report

	main (ef9f5ec)	#104 (63232f1)	+/-
Coverage	72.6%	72.6%	0.0%
Code to Test Ratio	1:0.7	1:0.7	0.0
Test Execution Time	51s	58s	+7s

Details

  |                     | main (ef9f5ec) | #104 (63232f1) | +/-  |
  |---------------------|----------------|----------------|------|
  | Coverage            |          72.6% |          72.6% | 0.0% |
  |   Files             |             17 |             17 |    0 |
  |   Lines             |           1936 |           1936 |    0 |
  |   Covered           |           1405 |           1405 |    0 |
  | Code to Test Ratio  |          1:0.7 |          1:0.7 |  0.0 |
  |   Code              |           3740 |           3740 |    0 |
  |   Test              |           2742 |           2742 |    0 |
- | Test Execution Time |            51s |            58s |  +7s |

Code coverage of files in pull request scope (72.7% → 72.7%)

Files	Coverage	+/-
operator.go	72.7%	0.0%

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Reported by octocov