gtls: fix indent to silence compiler warning

vtls/gtls.c: In function ‘Curl_gtls_data_pending’:
vtls/gtls.c:1429:3: error: this ‘if’ clause does not guard... [-Werror=misleading-indentation]
   if(conn->proxy_ssl[connindex].session &&
      ^~
      vtls/gtls.c:1433:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘if’
           return res;