Replace internal StringBuffer with StringBuilder

Author: garydgregory

src/changes/changes.xml

@@ -31,6 +31,7 @@
       <action type="fix" issue="CLI-334" dev="ggregory" due-to="Eric Pugh">Fix Javadoc pathing #280.</action>
       <action type="fix" issue="CLI-335" dev="ggregory" due-to="Claude Warren">Updated properties documentation #285.</action>
       <action type="fix" issue="CLI-336" dev="ggregory" due-to="Claude Warren, Gary Gregory">Deprecation not always reported #284.</action> 
+      <action type="fix" dev="ggregory" due-to="Gary Gregory">Replace internal StringBuffer with StringBuilder.</action>
       <!-- UPDATE -->
       <action type="update" dev="ggregory" due-to="Gary Gregory, Dependabot">Bump org.apache.commons:commons-parent from 70 to 72 #283.</action>
     </release>

src/main/java/org/apache/commons/cli/HelpFormatter.java

@@ -801,13 +801,13 @@ protected StringBuffer renderOptions(final StringBuffer sb, final int width, fin
         // sort options ascending
         int max = 0;
         int maxSince = showSince ? determineMaxSinceLength(options) + leftPad : 0;
-        final List<StringBuffer> prefixList = new ArrayList<>();
+        final List<StringBuilder> prefixList = new ArrayList<>();
         final List<Option> optList = options.helpOptions();
         if (getOptionComparator() != null) {
             Collections.sort(optList, getOptionComparator());
         }
         for (final Option option : optList) {
-            final StringBuffer optBuf = new StringBuffer();
+            final StringBuilder optBuf = new StringBuilder();
             if (option.getOpt() == null) {
                 optBuf.append(lpad).append("   ").append(getLongOptPrefix()).append(option.getLongOpt());
             } else {