Replace <tt> with <code> in javadoc, which HTML5 javadoc rejects

Fixes the maven-javadoc-plugin failure during release:perform on JDK 21.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: paulrutter

utils/src/main/java/org/apache/felix/utils/collections/MapToDictionary.java

@@ -23,8 +23,8 @@
 
 
 /**
- * This is a simple class that implements a <tt>Dictionary</tt>
- * from a <tt>Map</tt>. The resulting dictionary is immutatable.
+ * This is a simple class that implements a <code>Dictionary</code>
+ * from a <code>Map</code>. The resulting dictionary is immutatable.
 **/
 public class MapToDictionary extends Dictionary
 {

utils/src/main/java/org/apache/felix/utils/properties/InterpolationHelper.java

@@ -109,7 +109,7 @@ public static void performSubstitution(Map<String,String> properties,
      * <p>
      * This method performs property variable substitution on the
      * specified value. If the specified value contains the syntax
-     * <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt>
+     * <code>${&lt;prop-name&gt;}</code>, where <code>&lt;prop-name&gt;</code>
      * refers to either a configuration property or a system property,
      * then the corresponding property value is substituted for the variable
      * placeholder. Multiple variable placeholders may exist in the
@@ -140,7 +140,7 @@ public static String substVars(String val,
      * <p>
      * This method performs property variable substitution on the
      * specified value. If the specified value contains the syntax
-     * <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt>
+     * <code>${&lt;prop-name&gt;}</code>, where <code>&lt;prop-name&gt;</code>
      * refers to either a configuration property or a system property,
      * then the corresponding property value is substituted for the variable
      * placeholder. Multiple variable placeholders may exist in the
@@ -173,7 +173,7 @@ public static String substVars(String val,
      * <p>
      * This method performs property variable substitution on the
      * specified value. If the specified value contains the syntax
-     * <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt>
+     * <code>${&lt;prop-name&gt;}</code>, where <code>&lt;prop-name&gt;</code>
      * refers to either a configuration property or a system property,
      * then the corresponding property value is substituted for the variable
      * placeholder. Multiple variable placeholders may exist in the
@@ -206,7 +206,7 @@ public static String substVars(String val,
      * <p>
      * This method performs property variable substitution on the
      * specified value. If the specified value contains the syntax
-     * <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt>
+     * <code>${&lt;prop-name&gt;}</code>, where <code>&lt;prop-name&gt;</code>
      * refers to either a configuration property or a system property,
      * then the corresponding property value is substituted for the variable
      * placeholder. Multiple variable placeholders may exist in the