leveldb: Drop unnecessary patch

Remove patch no longer needed when we set TARGET_OS correctly.

packages/leveldb/port-port_posix.h.patch

@@ -1,12 +0,0 @@
-diff -u -r ../leveldb-1.20/port/port_posix.h ./port/port_posix.h
---- ../leveldb-1.20/port/port_posix.h	2017-03-02 01:08:02.000000000 +0100
-+++ ./port/port_posix.h	2017-09-22 22:18:21.814123643 +0200
-@@ -52,7 +52,7 @@
- 
- #if defined(OS_MACOSX) || defined(OS_SOLARIS) || defined(OS_FREEBSD) ||\
-     defined(OS_NETBSD) || defined(OS_OPENBSD) || defined(OS_DRAGONFLYBSD) ||\
--    defined(OS_ANDROID) || defined(OS_HPUX) || defined(CYGWIN)
-+    defined(OS_ANDROID) || defined(OS_HPUX) || defined(CYGWIN) || defined(__ANDROID__)
- // Use fread/fwrite/fflush on platforms without _unlocked variants
- #define fread_unlocked fread
- #define fwrite_unlocked fwrite