vtls: fix compile error

[georeth]

curl doesn't compile under my configuration.

vtls/openssl.c: In function ‘SSL_CTX_use_certificate_chain_blob’:
vtls/openssl.c:734: error: ‘in’ undeclared (first use in this function)
vtls/openssl.c:734: error: (Each undeclared identifier is reported only once
vtls/openssl.c:734: error: for each function it appears in.)

  Host setup:       x86_64-pc-linux-gnu
  Install prefix:   /home/zxz/usr
  Compiler:         gcc
   CFLAGS:          -Werror-implicit-function-declaration -O2 -Wno-system-headers -pthread
   CPPFLAGS:
   LDFLAGS:
   LIBS:            -lssl -lcrypto -lssl -lcrypto -lldap -lz -lrt

  curl version:     7.76.1
  SSL:              enabled (OpenSSL)
  SSH:              no      (--with-{libssh,libssh2})
  zlib:             enabled
  brotli:           no      (--with-brotli)
  zstd:             no      (--with-zstd)
  GSS-API:          no      (--with-gssapi)
  GSASL:            no      (libgsasl not found)
  TLS-SRP:          no      (--enable-tls-srp)
  resolver:         POSIX threaded
  IPv6:             enabled
  Unix sockets:     enabled
  IDN:              no      (--with-{libidn2,winidn})
  Build libcurl:    Shared=yes, Static=yes
  Built-in manual:  enabled
  --libcurl option: enabled (--disable-libcurl-option)
  Verbose errors:   enabled (--disable-verbose)
  Code coverage:    disabled
  SSPI:             no      (--enable-sspi)
  ca cert bundle:   /etc/pki/tls/certs/ca-bundle.crt
  ca cert path:     no
  ca fallback:      no
  LDAP:             enabled (OpenLDAP)
  LDAPS:            enabled
  RTSP:             enabled
  RTMP:             no      (--with-librtmp)
  Metalink:         no      (--with-libmetalink)
  PSL:              no      (libpsl not found)
  Alt-svc:          enabled
  HTTP1:            enabled (internal)
  HTTP2:            no      (--with-nghttp2, --with-hyper)
  HTTP3:            no      (--with-ngtcp2, --with-quiche)
  ECH:              no      (--enable-ech)
  Protocols:        DICT FILE FTP FTPS GOPHER GOPHERS HTTP HTTPS IMAP IMAPS LDAP LDAPS MQTT POP3 POP3S RTSP SMB SMBS SMTP SMTPS TELNET TFTP
  Features:         AsynchDNS HTTPS-proxy IPv6 Largefile NTLM NTLM_WB SSL UnixSockets alt-svc libz

[jay]

Thanks