Remove redundant SHA-1 code-path in TLS-1.2 handling of CrtVrfy

SHA-1 is no longer offered nor accepted for the client's CertificateVerify
message in TLS 1.2. See 0a64170.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 39edd83..b058e7c 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -4539,11 +4539,6 @@
             goto exit;
         }
 
-#if !defined(MBEDTLS_MD_SHA1)
-        if( MBEDTLS_MD_SHA1 == md_alg )
-            hash_start += 16;
-#endif
-
         /* Info from md_alg will be used instead */
         hashlen = 0;