license: update to use spdx syntax

rather than MIT/Apache-2.0, it should be `Apache-2.0 or MIT` to conform with SPDX syntax.

see examples in here, https://spdx.dev/learn/handling-license-info/#how

Author: chenrui333

Cargo.toml

@@ -6,7 +6,7 @@ description = "A high performance code minimap generator"
 categories = ["command-line-utilities"]
 homepage = "https://github.com/wfxr/code-minimap"
 keywords = ["minimap", "tool"]
-license = "MIT/Apache-2.0"
+license = "Apache-2.0 or MIT"
 exclude = ["/completions"]
 repository = "https://github.com/wfxr/code-minimap"
 edition = "2021"