[ISP] Changing fidl file to be not .test

This updates the ISP test fidl interface to comply with abarth's
fidl rules.

TEST: No functionality change.
Change-Id: I6660a9bf47e66ba7337c95245f9e7ade5f9dfb3d

zircon/system/fidl/fuchsia-camera-test/BUILD.gn

@@ -6,6 +6,6 @@ import("$zx/public/gn/fidl.gni")
 
 fidl_library("fuchsia-camera-test") {
   sources = [
-    "isp.test.fidl",
+    "isp.fidl",
   ]
 }