fix: Fix case by using Locale.ROOT

Author: bric3

lib/src/main/java/com/diffplug/spotless/java/TableTestFormatterStep.java

@@ -18,6 +18,7 @@
 import java.io.Serial;
 import java.io.Serializable;
 import java.lang.reflect.Constructor;
+import java.util.Locale;
 import java.util.Objects;
 
 import com.diffplug.spotless.FormatterFunc;
@@ -97,7 +98,7 @@ private State equalityState() {
 
 	public static String validateIndentStyle(String indentStyle) {
 		Objects.requireNonNull(indentStyle, "indentStyle");
-		String lower = indentStyle.toLowerCase();
+		String lower = indentStyle.toLowerCase(Locale.ROOT);
 		if (!lower.equals("space") && !lower.equals("tab")) {
 			throw new IllegalArgumentException("indentStyle must be 'space' or 'tab', got: " + indentStyle);
 		}

lib/src/tableTestFormatter/java/com/diffplug/spotless/glue/java/TableTestFormatterFunc.java

@@ -16,6 +16,7 @@
 package com.diffplug.spotless.glue.java;
 
 import java.io.File;
+import java.util.Locale;
 
 import org.tabletest.formatter.config.Config;
 import org.tabletest.formatter.config.EditorConfigProvider;
@@ -57,7 +58,7 @@ public TableTestFormatterFunc() {
 	 * @param indentSize  indent size (>= 0)
 	 */
 	public TableTestFormatterFunc(String indentStyle, int indentSize) {
-		this.sourceFallbackConfig = new Config(IndentStyle.valueOf(indentStyle.toUpperCase()), indentSize);
+		this.sourceFallbackConfig = new Config(IndentStyle.valueOf(indentStyle.toUpperCase(Locale.ROOT)), indentSize);
 	}
 
 	@Override