Remove ENTRY_LIMIT maximum checking and set it to 900

The number 900 is safely below github's limit of 1000 entries for a directory.
PRs to move tests can still decrease the sizes of various directories,
but adjusting the limit won't be neccessary any more.

In general, the limit is a bad tool to direct people to put tests into
fitting directories because when those are available, usually the limit
is not hit, while the limit is hit in directories that have a weak
substructure themselves.

src/tools/tidy/src/ui_tests.rs

@@ -7,10 +7,10 @@ use std::collections::HashMap;
 use std::fs;
 use std::path::{Path, PathBuf};
 
+const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
-const ENTRY_LIMIT: usize = 885;
-const ROOT_ENTRY_LIMIT: usize = 894;
 const ISSUES_ENTRY_LIMIT: usize = 1953;
+const ROOT_ENTRY_LIMIT: usize = 894;
 
 fn check_entries(tests_path: &Path, bad: &mut bool) {
     let mut directories: HashMap<PathBuf, usize> = HashMap::new();
@@ -46,9 +46,6 @@ fn check_entries(tests_path: &Path, bad: &mut bool) {
             );
         }
     }
-    if ENTRY_LIMIT > max {
-        tidy_error!(bad, "`ENTRY_LIMIT` is too high (is {ENTRY_LIMIT}, should be {max})");
-    }
     if ROOT_ENTRY_LIMIT > max_root {
         tidy_error!(
             bad,