Fix trivial typo in EVP_DigestVerifyInit doc

(cherry picked from commit b3883f77df33989b0d4298ca9a21d8595dd9a8c9)
Reviewed-by: NPaul Yang <yang.yang@baishancloud.com>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8319)

doc/man3/EVP_DigestVerifyInit.pod

@@ -28,8 +28,8 @@ EVP_PKEY_CTX of the verification operation will be written to B<*pctx>: this
 can be used to set alternative verification options. Note that any existing
 value in B<*pctx> is overwritten. The EVP_PKEY_CTX value returned must not be freed
 directly by the application if B<ctx> is not assigned an EVP_PKEY_CTX value before
-being passed to EVP_DigestSignInit() (which means the EVP_PKEY_CTX is created
-inside EVP_DigestSignInit() and it will be freed automatically when the
+being passed to EVP_DigestVerifyInit() (which means the EVP_PKEY_CTX is created
+inside EVP_DigestVerifyInit() and it will be freed automatically when the
 EVP_MD_CTX is freed).
 
 No B<EVP_PKEY_CTX> will be created by EVP_DigsetSignInit() if the passed B<ctx>