change severity of G-2310 to blocker

because using char instead of varchar2 can lead to
unexpected behavior or to a bug.

Author: PhilippSalvisberg

docs/4-language-usage/2-variables-and-types/3-character-data-types/g-2310.md

@@ -1,6 +1,6 @@
 # G-2310: Avoid using CHAR data type.
 
-!!! warning "Major"
+!!! bug "Blocker"
     Reliability
 
 ## Reason
@@ -17,6 +17,26 @@ end types_up;
 /
 ```
 
+Unexpected trailing spaces can lead to wrong results.
+
+```sql
+with
+   dept as (
+      select cast(department_name as varchar2(30 char)) as dname_vc2
+            ,cast(department_name as char(30 char)) as dname_char
+        from departments
+   )
+select count(*)
+  from dept
+ where dname_vc2 = dname_char;
+```
+
+```
+  COUNT(*)
+----------
+         0
+```
+
 ## Example (good)
 
 ``` sql