curl-openssl: pass argument to sed single-quoted

... instead of using an escaped double-quote. This is an attempt to make
this work better with ksh that otherwise would insist on a double
escape!

Reported-by: Randall S. Becker
Fixes curl#7758
Closes curl#7764

m4/curl-openssl.m4

@@ -66,7 +66,7 @@ AC_DEFUN([CURL_CHECK_OPENSSL_API_HEADERS], [
         ;;
       *)
         if test "$curl_cv_have_def_OPENSSL_VERSION_STR" = "yes"; then
-          ver=`echo $curl_cv_def_OPENSSL_VERSION_STR | sed s/\"//g`;
+          ver=`echo $curl_cv_def_OPENSSL_VERSION_STR | sed 's/"//g'`;
           tst_vermaj=`echo $ver | cut -d. -f1`
           tst_vermin=`echo $ver | cut -d. -f2`
           tst_verfix=`echo $ver | cut -d. -f3`