import: use CURLOPT_PROTOCOLS_STR with libcurl >= 7.85.0

import: use CURLOPT_PROTOCOLS_STR with libcurl >= 7.85.0

CURLOPT_PROTOCOLS [0] was deprecated in libcurl 7.85.0 with
CURLOPT_PROTOCOLS_STR [1] as a replacement, causing build warnings/errors:

../build/src/import/curl-util.c: In function ‘curl_glue_make’:
../build/src/import/curl-util.c:255:9: error: ‘CURLOPT_PROTOCOLS’ is deprecated: since 7.85.0. Use CURLOPT_PROTOCOLS_STR [-Werror=deprecated-declarations]
  255 |         if (curl_easy_setopt(c, CURLOPT_PROTOCOLS, CURLPROTO_HTTP|CURLPROTO_HTTPS|CURLPROTO_FILE) != CURLE_OK)
      |         ^~
In file included from ../build/src/import/curl-util.h:4,
                 from ../build/src/import/curl-util.c:6:
/usr/include/curl/curl.h:1749:3: note: declared here
 1749 |   CURLOPTDEPRECATED(CURLOPT_PROTOCOLS, CURLOPTTYPE_LONG, 181,
      |   ^~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Since there's no grace period between the two symbols, let's resort
to a light if-def-ery to resolve this.

[0] https://curl.se/libcurl/c/CURLOPT_PROTOCOLS.html
[1] https://curl.se/libcurl/c/CURLOPT_PROTOCOLS_STR.html