chore: revert excesive mutation timeouts (#439)

The new values are excessive and mutants won't timeout effectively
anymore, reverts changes done by this PR:


c0b7572#diff-b9d8f1106e1492b9a45476b57e61e1a54efaa4e8f464cf75f93fc40127678d59

Author: martintmk

scripts/mutants.rs

@@ -18,8 +18,8 @@ use ohno::AppError;
 use argh::FromArgs;
 
 const JOBS: u32 = 1;
-const BUILD_TIMEOUT_SEC: u32 = 6000;
-const TIMEOUT_SEC: u32 = 3000;
+const BUILD_TIMEOUT_SEC: u32 = 600;
+const TIMEOUT_SEC: u32 = 300;
 const MINIMUM_TEST_TIMEOUT_SEC: u32 = 60;
 
 /// Run mutation testing on the workspace