Windows .bats: use standard python invocation instead of py.exe launcher (#657)

* Use standard python invocation instead of py.exe launcher

* replace py.exe -> python also in protoc.bat

Co-authored-by: Karl Ljungkvist <karl.ljungkvist@dirac.com>
diff --git a/generator/protoc-gen-nanopb.bat b/generator/protoc-gen-nanopb.bat
index 48a4aa9..fa5bdd2 100644
--- a/generator/protoc-gen-nanopb.bat
+++ b/generator/protoc-gen-nanopb.bat
@@ -9,4 +9,4 @@
 :: --plugin= on the command line.
 
 set mydir=%~dp0
-py -3 "%mydir%\nanopb_generator.py" --protoc-plugin
+python "%mydir%\nanopb_generator.py" --protoc-plugin %*
diff --git a/generator/protoc.bat b/generator/protoc.bat
index cfd9e43..2538c94 100644
--- a/generator/protoc.bat
+++ b/generator/protoc.bat
@@ -5,5 +5,5 @@
 
 setLocal enableDelayedExpansion
 set mydir=%~dp0
-py -3 "%mydir%\protoc" %*
+python "%mydir%\protoc" %*
 exit /b %ERRORLEVEL%