Enable compression for Actions logs by default (#32013)

Close #31801. Follow #31761.

Since there are so many benefits of compression and there are no reports
of related issues after weeks, it should be fine to enable compression
by default.

modules/setting/actions.go

@@ -62,11 +62,11 @@ func (c logCompression) IsValid() bool {
 }
 
 func (c logCompression) IsNone() bool {
-	return c == "" || strings.ToLower(string(c)) == "none"
+	return strings.ToLower(string(c)) == "none"
 }
 
 func (c logCompression) IsZstd() bool {
-	return strings.ToLower(string(c)) == "zstd"
+	return c == "" || strings.ToLower(string(c)) == "zstd"
 }
 
 func loadActionsFrom(rootCfg ConfigProvider) error {