Update docs of lib.go/lib_no_cgo.go

(cherry picked from commit 79e4627)

Author: webmaster128

lib.go

@@ -1,6 +1,7 @@
 //go:build cgo && !nolink_libwasmvm
 
-// This file contains the part of the API that is exposed when cgo is enabled.
+// This file contains the part of the API that is exposed when libwasmvm
+// is available (i.e. cgo is enabled and nolink_libwasmvm is not set).
 
 package cosmwasm
 

lib_no_cgo.go

@@ -1,4 +1,5 @@
-// This file contains the part of the API that is exposed when cgo is disabled.
+// This file contains the part of the API that is exposed no matter if libwasmvm
+// is available or not. Symbols from lib.go are added conditionally.
 
 package cosmwasm