vad : remove shortform for --vad option in cli.cpp (#3145)

This commit removes the shortform for the --vad option in cli.cpp.

The motivation for this is that `-v` is often used for verbose or
version is many tools and this might cause confusion.

Refs: https://github.com/ggml-org/whisper.cpp/pull/3065#issuecomment-2873243334

examples/cli/cli.cpp

@@ -197,7 +197,7 @@ static bool whisper_params_parse(int argc, char ** argv, whisper_params & params
         else if (                  arg == "--grammar-rule")    { params.grammar_rule    = ARGV_NEXT; }
         else if (                  arg == "--grammar-penalty") { params.grammar_penalty = std::stof(ARGV_NEXT); }
         // Voice Activity Detection (VAD)
-        else if (arg == "-v"    || arg == "--vad")                         { params.vad                         = true; }
+        else if (                  arg == "--vad")                         { params.vad                         = true; }
         else if (arg == "-vm"   || arg == "--vad-model")                   { params.vad_model                   = ARGV_NEXT; }
         else if (arg == "-vt"   || arg == "--vad-threshold")               { params.vad_threshold               = std::stof(ARGV_NEXT); }
         else if (arg == "-vsd"  || arg == "--vad-min-speech-duration-ms")  { params.vad_min_speech_duration_ms  = std::stoi(ARGV_NEXT); }
@@ -276,7 +276,7 @@ static void whisper_print_usage(int /*argc*/, char ** argv, const whisper_params
     fprintf(stderr, "  --grammar-penalty N            [%-7.1f] scales down logits of nongrammar tokens\n",      params.grammar_penalty);
     // Voice Activity Detection (VAD) parameters
     fprintf(stderr, "\nVoice Activity Detection (VAD) options:\n");
-    fprintf(stderr, "  -v,        --vad                           [%-7s] enable Voice Activity Detection (VAD)\n",            params.vad ? "true" : "false");
+    fprintf(stderr, "             --vad                           [%-7s] enable Voice Activity Detection (VAD)\n",            params.vad ? "true" : "false");
     fprintf(stderr, "  -vm FNAME, --vad-model FNAME               [%-7s] VAD model path\n",                                   params.vad_model.c_str());
     fprintf(stderr, "  -vt N,     --vad-threshold N               [%-7.2f] VAD threshold for speech recognition\n",           params.vad_threshold);
     fprintf(stderr, "  -vspd N,   --vad-min-speech-duration-ms  N [%-7d] VAD min speech duration (0.0-1.0)\n",                params.vad_min_speech_duration_ms);