Fix presubmit

Author: fmeum

src/main/java/com/google/devtools/build/lib/unsafe/StringUnsafe.java

@@ -53,7 +53,8 @@ public final class StringUnsafe {
       constructor.setAccessible(true);
       CONSTRUCTOR = MethodHandles.lookup().unreflectConstructor(constructor);
 
-      var stringLookup = MethodHandles.privateLookupIn(String.class, MethodHandles.lookup());
+      MethodHandles.Lookup stringLookup =
+          MethodHandles.privateLookupIn(String.class, MethodHandles.lookup());
       VALUE_HANDLE = stringLookup.unreflectVarHandle(String.class.getDeclaredField("value"));
       CODE_HANDLE = stringLookup.unreflectVarHandle(String.class.getDeclaredField("coder"));
     } catch (ReflectiveOperationException e) {