Drop Python 2 packages

It would be nice to discontinue Python 2 support from LDAS Tools, allowing systems to install dev packages for LDAS Tools without installing the Python 2 stack.

 ldas-tools-al-devel           x86_64 2.6.7-1.el8   @lscsoft-production  17 M
 ldas-tools-al-swig            x86_64 2.6.9-1.el8   @lscsoft-production 527  
 ldas-tools-diskcacheAPI-devel x86_64 2.7.2-1.el8   @lscsoft-production  12 M
 ldas-tools-diskcacheAPI-swig  x86_64 2.6.10-1.el8  @lscsoft-production  28 k
 ldas-tools-filters-devel      x86_64 2.6.6-1.el8   @lscsoft-production 3.8 M
 ldas-tools-frameAPI-devel     x86_64 2.6.6-1.el8   @lscsoft-production 7.6 M
 ldas-tools-frameAPI-swig      x86_64 2.6.10-1.el8  @lscsoft-production  14 k
 ldas-tools-framecpp-c-devel   x86_64 2.8.1-1.el8   @lscsoft-production 1.7 M
 ldas-tools-framecpp-devel     x86_64 2.8.1-1.el8   @lscsoft-production  27 M
 ldas-tools-framecpp-swig      x86_64 2.6.12-1.el8  @lscsoft-production 125 k
 ldas-tools-ldasgen-devel      x86_64 2.7.3-1.el8   @lscsoft-production 5.1 M
 ldas-tools-ldasgen-swig       x86_64 2.6.9-1.el8   @lscsoft-production 1.6 k