docs: link OpenSSL's verify(1) manual page to know about -CAfile and -CApath options

The description of `--smtp-ssl-cert-path` in the git-send-email documentation
mentions consulting OpenSSL's verify(1) manual page for details about the
`-CAfile` and `-CApath` options. However, the way it was written was quite
confusing, and it didn't mention that OpenSSL's verify(1) is the manual page
to refer to.

Fix this by slightly rewording the description and also add a link to the
OpenSSL verify(1) manual page.

Signed-off-by: Aditya Garg <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: AdityaGarg8

Documentation/git-send-email.adoc

@@ -280,12 +280,14 @@ must be used for each option.
 	Path to a store of trusted CA certificates for SMTP SSL/TLS
 	certificate validation (either a directory that has been processed
 	by `c_rehash`, or a single file containing one or more PEM format
-	certificates concatenated together: see verify(1) -CAfile and
-	-CApath for more information on these). Set it to an empty string
-	to disable certificate verification. Defaults to the value of the
-	`sendemail.smtpSSLCertPath` configuration variable, if set, or the
-	backing SSL library's compiled-in default otherwise (which should
-	be the best choice on most platforms).
+	certificates concatenated together: see the description of the
+	`-CAfile` _<file>_ and the `-CApath` _<dir>_ options of
+	https://docs.openssl.org/master/man1/openssl-verify/
+	[OpenSSL's verify(1) manual page] for more information on these).
+	Set it to an empty string to disable certificate verification.
+	Defaults to the value of the `sendemail.smtpSSLCertPath` configuration
+	variable, if set, or the backing SSL library's compiled-in default
+	otherwise (which should be the best choice on most platforms).
 
 --smtp-user=<user>::
 	Username for SMTP-AUTH. Default is the value of `sendemail.smtpUser`;