wasm: remove emscripten condition for zlib

Change-Id: I67653ce15819e756bb3253da24c4761b3dd3c5bf
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

configure.json

@@ -1060,7 +1060,7 @@
         },
         "system-zlib": {
             "label": "Using system zlib",
-            "condition": "libs.zlib && config.emscripten",
+            "condition": "libs.zlib",
             "output": [ "privateFeature" ]
         },
         "future": {