shada: Do not export shada_read_file

Unlike some wrapper functions it is not used actually, so no need to export it.
Also removed ShadaPosition typedef which was not used.

src/nvim/shada.h

@@ -1,17 +1,6 @@
 #ifndef NVIM_SHADA_H
 #define NVIM_SHADA_H
 
-typedef long ShadaPosition;
-
-/// Flags for shada_read_file and children
-enum {
-  kShaDaWantInfo = 1,       ///< Load non-mark information
-  kShaDaWantMarks = 2,      ///< Load local file marks and change list
-  kShaDaForceit = 4,        ///< Overwrite info already read
-  kShaDaGetOldfiles = 8,    ///< Load v:oldfiles.
-  kShaDaMissingError = 16,  ///< Error out when os_open returns -ENOENT.
-};
-
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "shada.h.generated.h"
 #endif