Reduce golang requirement to go1.18

go1.21, the previous requirement, was released a few months ago, so not
all systems have adopted it.  go1.18 is old enough that most systems
should support it, but it introduces generics, which my testing code is
highly dependent on, so I can't easily go any earlier.

1 files changed, 1 insertions, 3 deletions

diff --git a/factors/prime_factorization.go b/factors/prime_factorization.go
index 52df2c1..f758448 100644
--- a/factors/prime_factorization.go
+++ b/factors/prime_factorization.go
@@ -2,7 +2,6 @@ package factors
 
 import (
 	"fmt"
-	"slices"
 	"strings"
 )
 
@@ -69,8 +68,7 @@ func (factors PrimeFactorization) Size() int {
 // String returns a string representation of the prime factorization,
 // which looks like "2^2 × 3".
 func (factors PrimeFactorization) String() string {
-	primesSorted := factors.Primes()
-	slices.Sort(primesSorted)
+	primesSorted := sortUints(factors.Primes())
 
 	parts := make([]string, 0, factors.Size())
 	for _, p := range primesSorted {