Fix another text block special case

Handle removing trailing whitespace when the closing delimiter is on the same
line as the final line of the text block.

Fixes #1205

PiperOrigin-RevId: 705218533

core/src/main/java/com/google/googlejavaformat/java/StringWrapper.java

@@ -225,7 +225,9 @@ private void indentTextBlocks(
           }
           if (i == lines.size() - 1) {
             String withoutDelimiter =
-                trimmed.substring(0, trimmed.length() - TEXT_BLOCK_DELIMITER.length());
+                trimmed
+                    .substring(0, trimmed.length() - TEXT_BLOCK_DELIMITER.length())
+                    .stripTrailing();
             if (!withoutDelimiter.stripLeading().isEmpty()) {
               output.append(withoutDelimiter).append('\\').append(separator).append(prefix);
             }

core/src/test/resources/com/google/googlejavaformat/java/testdata/I1205.input

@@ -0,0 +1,7 @@
+public interface Foo {
+
+  private static String foo =
+      """
+       foo\
+       bar """;
+}

core/src/test/resources/com/google/googlejavaformat/java/testdata/I1205.output

@@ -0,0 +1,8 @@
+public interface Foo {
+
+  private static String foo =
+      """
+      foo\
+      bar\
+      """;
+}