Default the English model's temperature to 0.3 (#223)

## Motivation

Human evaluations consistently prefer the English model at temperature
**0.3** over the current default **0.7**, and the change is free on
every objective axis we measured.

pocket_tts/main.py

@@ -20,7 +20,6 @@ from pocket_tts.default_parameters import (
     DEFAULT_FRAMES_AFTER_EOS,
     DEFAULT_LSD_DECODE_STEPS,
     DEFAULT_NOISE_CLAMP,
-    DEFAULT_TEMPERATURE,
     MAX_TOKEN_PER_CHUNK,
     get_default_text_for_language,
     get_default_voice_for_language,
@@ -261,8 +260,12 @@ def generate(
         int, typer.Option(help="Number of generation steps")
     ] = DEFAULT_LSD_DECODE_STEPS,
     temperature: Annotated[
-        float, typer.Option(help="Temperature for generation")
-    ] = DEFAULT_TEMPERATURE,
+        float | None,
+        typer.Option(
+            help="Temperature for generation. Defaults to the model's recommended "
+            "value from its config (0.3 for the English model, 0.7 otherwise)."
+        ),
+    ] = None,
     noise_clamp: Annotated[float, typer.Option(help="Noise clamp value")] = DEFAULT_NOISE_CLAMP,
     eos_threshold: Annotated[float, typer.Option(help="EOS threshold")] = DEFAULT_EOS_THRESHOLD,
     frames_after_eos: Annotated[