Default to production build

Now that the production build is fixed, I think it's better to default to it. Indeed, we want users installing JupyterLab to have the best experience using the interface and it means running the optimized production build.

This is especially true for extensions built with React because in dev mode, they will use the React's development bundle which is known to be much slower than the production one.

See also: #6804 (comment)

jupyterlab/labapp.py

@@ -61,8 +61,8 @@ class LabBuildApp(JupyterApp, DebugLogFileMixin):
     version = Unicode('', config=True,
         help="The version of the built application")
 
-    dev_build = Bool(True, config=True,
-        help="Whether to build in dev mode (defaults to dev mode)")
+    dev_build = Bool(False, config=True,
+        help="Whether to build in dev mode (defaults to prod mode)")
 
     pre_clean = Bool(False, config=True,
         help="Whether to clean before building (defaults to False)")

jupyterlab/labextensions.py

@@ -69,8 +69,8 @@ class BaseExtensionApp(JupyterApp, DebugLogFileMixin):
     should_build = Bool(True, config=True,
         help="Whether to build the app after the action")
 
-    dev_build = Bool(True, config=True,
-        help="Whether to build in dev mode (defaults to dev mode)")
+    dev_build = Bool(False, config=True,
+        help="Whether to build in dev mode (defaults to prod mode)")
 
     should_clean = Bool(False, config=True,
         help="Whether temporary files should be cleaned up after building jupyterlab")