[errorprone] Remove null check for value which cannot be null

See https://errorprone.info/bugpattern/ImpossibleNullComparison

Change-Id: I28dce4a107daa07784a9485c957a9df473f7d689

java/com/google/gitiles/Renderer.java

diff --git a/java/com/google/gitiles/Renderer.java b/java/com/google/gitiles/Renderer.java
index 3bf9754..dd08353 100644
--- a/java/com/google/gitiles/Renderer.java
+++ b/java/com/google/gitiles/Renderer.java
@@ -237,7 +237,7 @@
             .put("staticUrls", staticUrls.build())
             .put("SITE_TITLE", siteTitle);
     Optional<String> nonce = req.map((r) -> (String) r.getAttribute("nonce"));
-    if (nonce.isPresent() && nonce.get() != null) {
+    if (nonce.isPresent()) {
       ij.put("csp_nonce", nonce.get());
     }
     return getSauce().renderTemplate(templateName).setIj(ij.build());