Remove deprecated internal signatures of pgr_KSP

[cvvergara]

• Official in version: 2.0.0
• Deprecated internal function in v3.6.0:
  • _pgr_ksp(text,anyarray,anyarray,integer,boolean,boolean,boolean)
  • _pgr_ksp(text,bigint,bigint,integer,boolean,boolean)
  • _pgr_ksp(text,text,integer,boolean,boolean)

Tasks:

• Remove SQL deprecated signatures and functions
• pgtap tests to be done only on existing SQL functions
• Keeping deprecated internal C function
  • Moving to legacy will happen on v5