Remove CURL/CPR.

vendor/CPR/include/cpr/proxies.h

@@ -1,22 +0,0 @@
-#ifndef CPR_PROXIES_H
-#define CPR_PROXIES_H
-
-#include <initializer_list>
-#include <map>
-#include <string>
-
-namespace cpr {
-class Proxies {
-  public:
-    Proxies() = default;
-    Proxies(const std::initializer_list<std::pair<const std::string, std::string>>& hosts);
-
-    bool has(const std::string& protocol) const;
-    const std::string& operator[](const std::string& protocol);
-
-  protected:
-    std::map<std::string, std::string> hosts_;
-};
-} // namespace cpr
-
-#endif