doc: Remove file name section

This is already checked by test/lint/lint-files.py

There is no need to reword all linters into the dev notes.

Author: MarcoFalke

doc/developer-notes.md

@@ -1133,12 +1133,6 @@ Source code organization
 
   - *Rationale*: Shorter and simpler header files are easier to read and reduce compile time.
 
-- Use only the lowercase alphanumerics (`a-z0-9`), underscore (`_`) and hyphen (`-`) in source code filenames.
-
-  - *Rationale*: `grep`:ing and auto-completing filenames is easier when using a consistent
-    naming pattern. Potential problems when building on case-insensitive filesystems are
-    avoided when using only lowercase characters in source code filenames.
-
 - Every `.cpp` and `.h` file should `#include` every header file it directly uses classes, functions or other
   definitions from, even if those headers are already included indirectly through other headers.