[chore] Upgrade to Go 1.24 (#4187)

* Set `go.mod` to 1.24 now that it's been out for 3 months.
* Update all the test to use `testing.T.Context()`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4187
Co-authored-by: Daenney <git@noreply.sourcery.dny.nu>
Co-committed-by: Daenney <git@noreply.sourcery.dny.nu>

internal/db/bundb/errors_test.go

@@ -18,7 +18,6 @@
 package bundb_test
 
 import (
-	"context"
 	"errors"
 	"testing"
 
@@ -38,7 +37,7 @@ func (suite *ErrorsTestSuite) TestErrorAlreadyExists() {
 	}
 
 	var (
-		ctx           = context.Background()
+		ctx           = suite.T().Context()
 		initialFollow = &gtsmodel.Follow{
 			ID:              "01HD11D8JH5V64GJRFDA7VFNDX",
 			URI:             "https://example.org/unique_uri",