Compare strings with strings.EqualFold

[Juneezee]

This PR fixes a Staticcheck warning (https://staticcheck.dev/docs/checks/#SA6005). Comparing two strings to the same case with strings.ToLower and strings.ToUpper is more computational expensive than strings.EqualFold.

Sample benchmark:

func BenchmarkToUpperSingle(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if strings.ToUpper("foobar") != "FOOBAR" {
			b.Fail()
		}
	}
}

func BenchmarkToUpperDouble(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if strings.ToUpper("foobar") != strings.ToUpper("FOOBAR") {
			b.Fail()
		}
	}
}

func BenchmarkToLowerSingle(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if strings.ToLower("FOOBAR") != "foobar" {
			b.Fail()
		}
	}
}

func BenchmarkToLowerDouble(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if strings.ToLower("FOOBAR") != strings.ToLower("foobar") {
			b.Fail()
		}
	}
}

func BenchmarkEqualFold(b *testing.B) {
	for i := 0; i < b.N; i++ {
		if !strings.EqualFold("FOOBAR", "foobar") {
			b.Fail()
		}
	}
}

Result:

goos: linux
goarch: amd64
pkg: github.com/dolthub/dolt/go
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkToUpperSingle-16    	 9589896	       113.8 ns/op	       8 B/op	       1 allocs/op
BenchmarkToUpperDouble-16    	 7097330	       155.9 ns/op	       8 B/op	       1 allocs/op
BenchmarkToLowerSingle-16    	12346219	       106.5 ns/op	       8 B/op	       1 allocs/op
BenchmarkToLowerDouble-16    	 8084006	       143.6 ns/op	       8 B/op	       1 allocs/op
BenchmarkEqualFold-16        	63650023	        18.76 ns/op	       0 B/op	       0 allocs/op
PASS
ok  	github.com/dolthub/dolt/go	6.456s

[jycor]

Thanks for the changes.
Everything looks great!