Adjust symbol to expose version 3 as needed by some binaries (e.g. Spotify).

diff -Nur curl-7.78.0.old/lib/libcurl.vers.in curl-7.78.0/lib/libcurl.vers.in
--- curl-7.78.0.old/lib/libcurl.vers.in	2020-11-04 09:59:52.000000000 -0300
+++ curl-7.78.0/lib/libcurl.vers.in	2021-09-13 23:17:52.025514380 -0300
@@ -6,7 +6,7 @@
     _save*;
 };
 
-CURL_@CURL_LT_SHLIB_VERSIONED_FLAVOUR@4
+CURL_@CURL_LT_SHLIB_VERSIONED_FLAVOUR@3
 {
   global: curl_*;
   local: *;