Remove redundant procedure constraints and combine some procedure normative text

[aury6623]

For the normative text part, I thought it was just more concise to combine those two paragraphs.

For the constraint part, the constraints about functions and subroutines are redundant because of this constraint:

Constraint: Except for PURE, SIMPLE, and ELEMENTAL
            attributes, the characteristics of all specifications of a
            deferred procedure shall be consistent.

From F2023:

The characteristics of a procedure are the classification of the procedure as a function or subroutine, ...

Since the function or subroutine-ness are characteristics, the constraint written above covers both of the removed constraints in this edit.