Use ElementsMatch to ignore order

[kevinv-stripe]

Fixes a non-deterministic failing test TestMapKeys.

This change switches the test comparison to require.ElementsMatch to compare slices, which ignores ordering, since iteration order over maps is not specified and is not guaranteed to be the same from one iteration to the next.

https://go.dev/ref/spec#For_statements

Verified that consecutive tests now pass:

➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.169s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.152s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.160s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.156s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.159s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.141s
➜  smokescreen git:(kevinv/fix-test-map-keys) ✗ go test ./pkg/smokescreen/metrics/... -count=1
ok  	github.com/stripe/smokescreen/pkg/smokescreen/metrics	0.159s

[github-actions]

Pull Request Test Coverage Report for Build 5073174494

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 62.512%

---

Totals
Change from base Build 5024495973:	0.0%
Covered Lines:	1294
Relevant Lines:	2070

---

💛 - Coveralls