patch 8.2.3961: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/gui_photon.c b/src/gui_photon.c
index ea8e5e4..d48a153 100644
--- a/src/gui_photon.c
+++ b/src/gui_photon.c
@@ -2955,7 +2955,7 @@
     }
 
     if (report_error)
-	semsg(e_font, vim_font_name);
+	semsg(e_unknown_font_str, vim_font_name);
 
     return FAIL;
 }