Remove some unused MySQL 5.6 code (#16465)

Signed-off-by: Graham Campbell <hello@gjcampbell.co.uk>

Author: GrahamCampbell

go/mysql/binlog_event.go

@@ -158,7 +158,7 @@ type BinlogFormat struct {
 	HeaderSizes []byte
 
 	// ServerVersion is the name of the MySQL server version.
-	// It starts with something like 5.6.33-xxxx.
+	// It starts with something like 8.0.34-xxxx.
 	ServerVersion string
 
 	// FormatVersion is the version number of the binlog file format.

go/mysql/capabilities/capability.go

@@ -40,7 +40,6 @@ const (
 	InstantAddDropColumnFlavorCapability                                // Adding/dropping column in any position/ordinal.
 	InstantChangeColumnDefaultFlavorCapability                          //
 	InstantExpandEnumCapability                                         //
-	MySQLJSONFlavorCapability                                           // JSON type supported
 	MySQLUpgradeInServerFlavorCapability                                //
 	DynamicRedoLogCapacityFlavorCapability                              // supported in MySQL 8.0.30 and above: https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-30.html
 	DisableRedoLogFlavorCapability                                      // supported in MySQL 8.0.21 and above: https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-21.html
@@ -89,8 +88,6 @@ func MySQLVersionHasCapability(serverVersion string, capability FlavorCapability
 	}
 	// Capabilities sorted by version.
 	switch capability {
-	case MySQLJSONFlavorCapability:
-		return atLeast(5, 7, 0)
 	case InstantDDLFlavorCapability,
 		InstantExpandEnumCapability,
 		InstantAddLastColumnFlavorCapability,

go/mysql/capabilities/capability_test.go

@@ -145,7 +145,7 @@ func TestMySQLVersionCapableOf(t *testing.T) {
 			isCapable:  false,
 		},
 		{
-			version:    "5.6.7",
+			version:    "5.7.29",
 			capability: InstantDDLFlavorCapability,
 			isCapable:  false,
 		},
@@ -154,16 +154,6 @@ func TestMySQLVersionCapableOf(t *testing.T) {
 			capability: TransactionalGtidExecutedFlavorCapability,
 			isCapable:  false,
 		},
-		{
-			version:    "5.6.7",
-			capability: MySQLJSONFlavorCapability,
-			isCapable:  false,
-		},
-		{
-			version:    "5.7.29",
-			capability: MySQLJSONFlavorCapability,
-			isCapable:  true,
-		},
 		{
 			version:    "8.0.30",
 			capability: DynamicRedoLogCapacityFlavorCapability,

go/mysql/flavor_mysqlgr_test.go

@@ -84,7 +84,7 @@ func TestMysqlGRSupportCapability(t *testing.T) {
 			isCapable:  false,
 		},
 		{
-			version:    "5.6.7",
+			version:    "5.7.29",
 			capability: capabilities.InstantDDLFlavorCapability,
 			isCapable:  false,
 		},
@@ -93,16 +93,6 @@ func TestMysqlGRSupportCapability(t *testing.T) {
 			capability: capabilities.TransactionalGtidExecutedFlavorCapability,
 			isCapable:  false,
 		},
-		{
-			version:    "5.6.7",
-			capability: capabilities.MySQLJSONFlavorCapability,
-			isCapable:  false,
-		},
-		{
-			version:    "5.7.29",
-			capability: capabilities.MySQLJSONFlavorCapability,
-			isCapable:  true,
-		},
 		{
 			version:    "8.0.30",
 			capability: capabilities.DynamicRedoLogCapacityFlavorCapability,

go/mysql/flavor_test.go

@@ -53,11 +53,6 @@ func TestServerVersionCapableOf(t *testing.T) {
 			capability: capabilities.TransactionalGtidExecutedFlavorCapability,
 			isCapable:  false,
 		},
-		{
-			version:    "5.7.29",
-			capability: capabilities.MySQLJSONFlavorCapability,
-			isCapable:  true,
-		},
 		{
 			version:    "8.0.30",
 			capability: capabilities.DynamicRedoLogCapacityFlavorCapability,