Update minimal Flutter version to 3.38.3

Bump the required Flutter version from 3.38.2 to 3.38.3 in both .fvmrc and flutter_base.py to ensure compatibility with the latest release.

Author: FeodorFitsner

.fvmrc

@@ -1,3 +1,3 @@
 {
-  "flutter": "3.38.2"
+  "flutter": "3.38.3"
 }

sdk/python/packages/flet-cli/src/flet_cli/commands/flutter_base.py

@@ -20,7 +20,7 @@
 PYODIDE_ROOT_URL = "https://cdn.jsdelivr.net/pyodide/v0.27.7/full"
 DEFAULT_TEMPLATE_URL = "gh:flet-dev/flet-build-template"
 
-MINIMAL_FLUTTER_VERSION = version.Version("3.38.2")
+MINIMAL_FLUTTER_VERSION = version.Version("3.38.3")
 
 no_rich_output = get_bool_env_var("FLET_CLI_NO_RICH_OUTPUT")