What is ILS CLASS in this airport NOTAM?
This is a change in the ILS Facility Classification code. In your example the code is I/C/2 for ILS with GP, which means:

The ILS category is CAT I
Quality of Course C, which means localizer performance follows performance requirements until 100ft
Integrity level 2 (see ICAO Annex 10, Volume I for details)

The changes can also be found in the Kazakhstan eAIP UAII AD 2.19.
Here is a detailed description of the three codes in the classification by ICAO:

ILS FACILITY CLASSIFICATION AND DOWNGRADING
The  ILS  facility  classification  system  provides  a  more  comprehensive  method  of  describing  ILS  performance  than  the  simple  CAT  I/II/III  classification.  An  example  of  an  ILS  facility  classification  is  “III/E/4”.  ILS  facility  classification  is  described in Annex 10, Volume 1. A facility’s “class” of performance is defined by using three characters as follows:
a)    The first group of characters (I or II or III) indicates conformance to the facility performance category standards contained in Annex 10, Volume I. This character indicates if the ground equipment meets a facility performance Category I, II or III.
b)    The  second  group  of  a  single  character  defines  the  ILS  point  (Figure  C-1)  to  which  the  localizer  conforms  to  the  facility  performance  Category  II/III  course  structure  tolerances.  These  classifications  indicate ILS conformance to a physical location on the approach or runway as follows:

A:    7.5 km (4 NM) before the threshold;
B:    1 050 m (3 500 ft) before the threshold (CAT I decision point);
C:    Glide path altitude of 100 ft HATh (CAT II decision point);
T:    Threshold;
D:    900 m (3 000 ft) beyond the threshold (facility performance category III requirement only);
E:    600 m (2 000 ft) before the runway end (facility performance category III requirement only).

c)     The  third  group  of  a  single  character  indicates  the  level  of  integrity  and  continuity  of  service.  It  is  generally  accepted,  irrespective  of  the  operational  objective,  that  the  average  rate  of  a  fatal  accident  during landing due to failures or shortcomings in the whole system, comprising the ground equipment, the  aircraft  and  the  pilot,  should  not  exceed  $1 \times 10^{–7}$.  This  criterion  is  frequently  referred  to  as  the  global risk factor. In Category III operations, this objective should be inherent in the whole system. In this  context  it  is  of  the  utmost  importance  to  endeavour  to  achieve  the  highest  level  of  integrity  and  continuity  of  service  of  the  ground  equipment.  Integrity  is  needed  to  ensure  that  an  aircraft  on  approach  will  have  a  low  probability  of  receiving  false  guidance;  continuity  of  service  is  needed  to  ensure that an aircraft in the final stages of approach will have a low probability of being deprived of a guidance  signal.  Integrity  and  continuity  of  service  requirements  are  defined  in  Annex  10,  Volume  I,  Chapter 3, 3.1.3.12, for the localizer and Chapter 3, 3.1.5.8, for the glide path.

(ICAO Manual of All-Weather Operations)