Slip resistance check update according to SP 16

The last revision of the Russian code affected the friction-type bolts check in IDEA StatiCa Connection.

The formula for the design tensile strength of a high-strength bolt Rbh = 0.7 · Rbun is replaced by design tensile strength Rbt according to SP 16, Table 5.

The updated formula can look like this:

Updated in Expert and Enhanced edition of IDEA StatiCa Steel.