Clean up a dead variable in invoke canonicalizer.

Change-Id: I7d027b8488015abdac57d72390c3a57e24fbd1c1
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/IdempotentFunctionCallCanonicalizer.java b/src/main/java/com/android/tools/r8/ir/optimize/IdempotentFunctionCallCanonicalizer.java
index 6e958f1..c99f27a 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/IdempotentFunctionCallCanonicalizer.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/IdempotentFunctionCallCanonicalizer.java
@@ -121,7 +121,6 @@
         if (current.outValue().hasLocalInfo()) {
           continue;
         }
-        DexMethod invokedMethod = invoke.getInvokedMethod();
         // Interested in known-to-be idempotent methods.
         if (!isIdempotentLibraryMethodInvoke(invoke)) {
           if (!appView.enableWholeProgramOptimizations()) {