Fix config types

Signed-off-by: Asai Neko <sugar@sne.moe>

config.default.yaml

@@ -24,7 +24,6 @@ email:
     port:
     username:
     password:
-    from:
     security:
     insecure_skip_verify:
 secrets:

config/types.go

@@ -45,7 +45,6 @@ type email struct {
 	Port               string `yaml:"port"`
 	Username           string `yaml:"username"`
 	Password           string `yaml:"password"`
-	From               string `yaml:"from"`
 	Security           string `yaml:"security"`
 	InsecureSkipVerify bool   `yaml:"insecure_skip_verify"`
 }