Reverts "Disable Impeller when the manifest explicitly disables it (#53108)" (#53124)

Reverts: #53108
Initiated by: jonahwilliams
Reason for reverting: Probably --no-enable-impeller isn't working
Original PR Author: jiahaog

Reviewed By: {jonahwilliams}

This change reverts the following previous change:
After #53099, impeller is always enabled, even if the manifest disables it using `io.flutter.embedding.android.EnableImpeller`. 

This PR causes it to respect the manifest value if it is explicitly disabled.

Fixes b/343603270

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: auto-submit[bot]

shell/platform/android/io/flutter/embedding/engine/loader/FlutterLoader.java

@@ -340,10 +340,8 @@ public void ensureInitializationComplete(
       shellArgs.add("--prefetched-default-font-manager");
 
       if (metaData != null) {
-        if (metaData.getBoolean(ENABLE_IMPELLER_META_DATA_KEY, true)) {
+        if (metaData.getBoolean(ENABLE_IMPELLER_META_DATA_KEY, false)) {
           shellArgs.add("--enable-impeller");
-        } else {
-          shellArgs.add("--enable-impeller=false");
         }
         if (metaData.getBoolean(ENABLE_VULKAN_VALIDATION_META_DATA_KEY, false)) {
           shellArgs.add("--enable-vulkan-validation");