config : fallback to 22 instead of None

The configparser fallback option was None set it to use 22 instead as
None doesn't make sense

src/unisync/config.py

@@ -16,7 +16,7 @@ class ServerConfig:
     sshargs: str = ""
     hostname: str = ""
     ip: str = ""
-    port: int | None = 22
+    port: int = 22
 
     def __post_init__(self):
         """
@@ -85,7 +85,7 @@ def load_config(config_path:str) -> Config:
             config.get(server_section, "sshargs", fallback=""),
             config.get(server_section, "hostname", fallback=""),
             config.get(server_section, "ip", fallback=""),
-            config.getint(server_section, "port", fallback=None)
+            config.getint(server_section, "port", fallback=22)
         )
     roots_config = RootsConfig(
             config.get(roots_section, "local"),