[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/ap/extractfocus_test.go

@@ -18,7 +18,6 @@
 package ap_test
 
 import (
-	"context"
 	"encoding/json"
 	"fmt"
 	"testing"
@@ -33,7 +32,7 @@ type ExtractFocusTestSuite struct {
 }
 
 func (suite *ExtractFocusTestSuite) TestExtractFocus() {
-	ctx := context.Background()
+	ctx := suite.T().Context()
 
 	type test struct {
 		data    string