Upgrade code by using instance-of pattern matching

Updated the existing code with Pattern matching to eliminate  explicit
type cast

Author: RagiGeorge

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/themes/ColorDefinition.java

@@ -137,8 +137,8 @@ public boolean isEditable() {
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj instanceof ColorDefinition) {
-			return getId().equals(((ColorDefinition) obj).getId());
+		if (obj instanceof ColorDefinition colorDef) {
+			return getId().equals(colorDef.getId());
 		}
 		return false;
 	}

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/themes/FontDefinition.java

@@ -116,8 +116,8 @@ public boolean isEditable() {
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj instanceof FontDefinition) {
-			return getId().equals(((FontDefinition) obj).getId());
+		if (obj instanceof FontDefinition fontDef) {
+			return getId().equals(fontDef.getId());
 		}
 		return false;
 	}

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/themes/ThemeElementCategory.java

@@ -105,8 +105,8 @@ public String getParentId() {
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj instanceof ThemeElementCategory) {
-			return getId().equals(((ThemeElementCategory) obj).getId());
+		if (obj instanceof ThemeElementCategory category) {
+			return getId().equals(category.getId());
 		}
 		return false;
 	}