Fix 2 warnings

This fixes 2 simple warnings when compiling:

warning: the item `HashMap` is imported redundantly                                      
   --> database/src/fs.rs:481:13                                                                                                                                                   
    |                                                                                    
1   | use std::collections::HashMap;                                                     
    |     ------------------------- the item `HashMap` is already imported here
...                                  
481 |         use std::collections::HashMap;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^
    |                                                                                    
    = note: #[warn(unused_imports)] on by default   
                                            
warning: the feature `try_from` has been stable since 1.34.0 and no longer requires an attribute to enable                                                                         
 --> database/src/lib.rs:3:12                                                                                                                                                      
  |                        
3 | #![feature(try_from)]          
  |            ^^^^^^^^                                                                  
  |                                                                                                                                                                                
  = note: #[warn(stable_features)] on by default