libstore/filetransfer: Add HttpMethod::PUT

This got lost in f1968ea38e and
now we had incorrect logs that confused "downloading" when we were
in fact "uploading" things.

src/libstore/s3-binary-cache-store.cc

@@ -101,6 +101,7 @@ std::string
 S3BinaryCacheStore::uploadPart(std::string_view key, std::string_view uploadId, uint64_t partNumber, std::string data)
 {
     auto req = makeRequest(key);
+    req.method = HttpMethod::PUT;
     req.setupForS3();
 
     auto url = req.uri.parsed();