GN: Fix common_audio linking on iOS

The invalid condition made the test be included for iOS, which
fails linking.

BUG=webrtc:5949, webrtc:5544
NOTRY=True

Review-Url: https://codereview.webrtc.org/2291023002
Cr-Commit-Position: refs/heads/master@{#13970}

webrtc/common_audio/BUILD.gn

@@ -284,7 +284,7 @@ if (rtc_include_tests) {
     ]
 
     # Does not compile on iOS for arm: webrtc:5544.
-    if (!is_ios || target_cpu != "arm" || target_cpu != "arm64") {
+    if (!is_ios || target_cpu != "arm") {
       sources += [ "resampler/sinc_resampler_unittest.cc" ]
     }