Fix -Wunused-variable compiler warning

frameworks/base/tools/aapt2/link/ManifestFixer.cpp:341:23: error: unused variable 'attr' [-Werror,-Wunused-variable]
  341 |   if (xml::Attribute* attr = el->FindAttribute(xml::kSchemaAndroid, "glEsVersion")) {
      |                       ^~~~

Test: presubmit
Change-Id: Icec4737a5f8076173a2aff54532a79fa123df326
diff --git a/tools/aapt2/link/ManifestFixer.cpp b/tools/aapt2/link/ManifestFixer.cpp
index c4f6e70..0b16e2c 100644
--- a/tools/aapt2/link/ManifestFixer.cpp
+++ b/tools/aapt2/link/ManifestFixer.cpp
@@ -338,7 +338,7 @@
   }
 
   bool has_gl_es_version = false;
-  if (xml::Attribute* attr = el->FindAttribute(xml::kSchemaAndroid, "glEsVersion")) {
+  if (el->FindAttribute(xml::kSchemaAndroid, "glEsVersion")) {
     if (has_name) {
       diag->Error(android::DiagMessage(el->line_number)
                   << "cannot define both android:name and android:glEsVersion in <uses-feature>");