enable thread_local_initializer_can_be_made_const

There's barely enough room in the commit title for this lint's name...

Cargo.toml

@@ -72,7 +72,6 @@ wildcard_dependencies = "warn"
 missing_errors_doc = "allow"
 missing_panics_doc = "allow"
 
-thread_local_initializer_can_be_made_const = "allow"
 unnecessary_to_owned = "allow"
 
 [package]

src/database/abstraction/sqlite.rs

@@ -16,9 +16,9 @@ use crate::{database::Config, Result};
 
 thread_local! {
     static READ_CONNECTION: RefCell<Option<&'static Connection>> =
-        RefCell::new(None);
+        const { RefCell::new(None) };
     static READ_CONNECTION_ITERATOR: RefCell<Option<&'static Connection>> =
-        RefCell::new(None);
+        const { RefCell::new(None) };
 }
 
 struct PreparedStatementIterator<'a> {