Fix clippy warning:

[marxin]

warning: this manual char comparison can be written more succinctly
   --> src/rpm/filecaps.rs:120:37
    |
120 |         let index = match part.find(|c| c == '+' || c == '-' || c == '=') {
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using an array of `char`: `['+', '-', '=']`