misc: fix code quality findings

- httpsrr: drop redundant checks.
  Follow-up to 809dda3a37 #21354
- httpsrr.h: drop obsolete comment.
  Follow-up to 2b3dfb4ad4 #21175
- ws: drop redundant check in `curl_ws_start_frame()`.
  Follow-up to 37cecfc7b9 #17683
- ws: fix typo in comment.
- tool_operate: fix VMS build. (broken since 2019-07-20, v7.66.0)
  Follow-up to b889408500 #3804

Pointed out by Copilot Code Quality

Closes #21393

lib/httpsrr.h

@@ -52,7 +52,7 @@ struct Curl_https_rrinfo {
   size_t ipv6hints_len;
   unsigned char alpns[MAX_HTTPSRR_ALPNS]; /* keytag = 1 */
   /* store parsed alpnid entries in the array, end with ALPN_none */
-  uint16_t port; /* -1 means not set */
+  uint16_t port;
   uint16_t priority;
   BIT(no_def_alpn); /* keytag = 2 */
   BIT(mandatory); /* keytag = 0 */