Update instrumentation/servlet/servlet-common/bootstrap/src/main/java…

…/io/opentelemetry/javaagent/bootstrap/servlet/InjectionState.java

Co-authored-by: Mateusz Rzeszutek <mrzeszutek@splunk.com>

instrumentation/servlet/servlet-common/bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/servlet/InjectionState.java

@@ -8,7 +8,7 @@
 // this is shared by both ServletOutputStream and PrintWriter injection
 public class InjectionState {
   private static final int HEAD_TAG_WRITTEN_FAKE_VALUE = -1;
-  private static final int HEAD_TAG_PREFIX_LENGTH = 4;
+  private static final int HEAD_TAG_PREFIX_LENGTH = "<head".length();
   private final SnippetInjectingResponseWrapper wrapper;
   private int headTagBytesSeen = 0;