replace assert.h with cassert

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/config/File.cxx

@@ -35,7 +35,7 @@
 #include "fs/io/BufferedReader.hxx"
 #include "Log.hxx"
 
-#include <assert.h>
+#include <cassert>
 
 static constexpr char CONF_COMMENT = '#';
 

src/config/Path.cxx

@@ -24,7 +24,8 @@
 #include "fs/StandardDirectory.hxx"
 #include "util/RuntimeError.hxx"
 
-#include <assert.h>
+#include <cassert>
+
 #include <string.h>
 
 #ifndef _WIN32