Remove unused assignment.

This fixes the lint errors:

[UnusedVariable] This assignment to the local variable 'randomSpi' is never read.
[UnusedVariable] This assignment to the local variable 'droidSpi' is never read.

Test: test-only change
Change-Id: I34bd3c892f56806dae99c05bc190572c18d9b1e8
diff --git a/tests/cts/net/src/android/net/cts/IpSecManagerTest.java b/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
index 4791eab..9496787 100644
--- a/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
@@ -124,7 +124,7 @@
     @Test
     public void testAllocSpi() throws Exception {
         for (InetAddress addr : GOOGLE_DNS_LIST) {
-            SecurityParameterIndex randomSpi = null, droidSpi = null;
+            SecurityParameterIndex randomSpi, droidSpi;
             randomSpi = mISM.allocateSecurityParameterIndex(addr);
             assertTrue(
                     "Failed to receive a valid SPI",