badwords: check indented lines in source code, fix fallouts

- badwords.pl: add `-a` option to check all lines in source code files.
  Before this patch indented lines were skipped (to avoid Markdown code
  fences.)
- GHA/checksrc: use `-a` when verifying the source code.
- GHA/checksrc: disable `So` and `But` rules for source code.
- GHA/checksrc: add docs/examples to the verified sources.
- badwords.txt: delete 4 duplicates.
- badwords.txt: group and sort contractions.
- badwords.txt: allow ` url = `, `DIR`, `<file name`.

Closes #19536

lib/vtls/openssl.c

@@ -1688,7 +1688,7 @@ static CURLcode client_cert(struct Curl_easy *data,
         failf(data,
               "could not load PEM client certificate from %s, " OSSL_PACKAGE
               " error %s, "
-              "(no key found, wrong pass phrase, or wrong file format?)",
+              "(no key found, wrong passphrase, or wrong file format?)",
               (cert_blob ? "CURLOPT_SSLCERT_BLOB" : cert_file),
               ossl_strerror(ERR_get_error(), error_buffer,
                             sizeof(error_buffer)) );
@@ -1708,7 +1708,7 @@ static CURLcode client_cert(struct Curl_easy *data,
         failf(data,
               "could not load ASN1 client certificate from %s, " OSSL_PACKAGE
               " error %s, "
-              "(no key found, wrong pass phrase, or wrong file format?)",
+              "(no key found, wrong passphrase, or wrong file format?)",
               (cert_blob ? "CURLOPT_SSLCERT_BLOB" : cert_file),
               ossl_strerror(ERR_get_error(), error_buffer,
                             sizeof(error_buffer)) );
@@ -5154,7 +5154,7 @@ CURLcode Curl_ossl_check_peer_cert(struct Curl_cfilter *cf,
 #endif
 
   if(data->set.ssl.certinfo && !octx->reused_session) {
-    /* asked to gather certificate info. Reused sessions don't have cert
+    /* asked to gather certificate info. Reused sessions do not have cert
        chains */
     result = ossl_certchain(data, octx->ssl);
     if(result)
@@ -5684,7 +5684,7 @@ static CURLcode ossl_get_channel_binding(struct Curl_easy *data, int sockindex,
 
   cert = SSL_get1_peer_certificate(octx->ssl);
   if(!cert)
-    /* No server certificate, don't do channel binding */
+    /* No server certificate, do not do channel binding */
     return CURLE_OK;
 
   if(!OBJ_find_sigid_algs(X509_get_signature_nid(cert), &algo_nid, NULL)) {