syntax: detect bash 5.2 rather than 5.1

5.2 was released in late 2022.
We track any changes we might need in our parser via #921,
and aside from that all existing bash tests still pass with 5.2.

syntax/parser.go

@@ -31,7 +31,7 @@ const (
 	// LangBash corresponds to the GNU Bash language, as described in its
 	// manual at https://www.gnu.org/software/bash/manual/bash.html.
 	//
-	// We currently follow Bash version 5.1.
+	// We currently follow Bash version 5.2.
 	//
 	// Its string representation is "bash".
 	LangBash LangVariant = iota

syntax/parser_test.go

@@ -163,8 +163,8 @@ func TestMain(m *testing.M) {
 }
 
 var (
-	storedHasBash51 bool
-	onceHasBash51   sync.Once
+	storedHasBash52 bool
+	onceHasBash52   sync.Once
 
 	storedHasDash059 bool
 	onceHasDash059   sync.Once
@@ -174,10 +174,10 @@ var (
 )
 
 func hasBash51(tb testing.TB) {
-	onceHasBash51.Do(func() {
-		storedHasBash51 = cmdContains("version 5.1", "bash", "--version")
+	onceHasBash52.Do(func() {
+		storedHasBash52 = cmdContains("version 5.2", "bash", "--version")
 	})
-	if !storedHasBash51 {
+	if !storedHasBash52 {
 		tb.Skipf("bash 5.1 required to run")
 	}
 }