style: format code with Go fmt and Gofumpt

This commit fixes the style issues introduced in da641a8 according to the output
from Go fmt and Gofumpt.

Details: https://github.com/gogs/gogs/pull/8111

internal/context/context.go

@@ -301,7 +301,7 @@ func Contexter(store Store) flamego.Handler {
 				flash = f
 			}
 		}
-		
+
 		c := &Context{
 			Context:        fctx,
 			Template:       tpl,