CLN: fix compiler warnings in tzconversion.pyx
Fixes 
```
pandas/_libs/tslibs/tzconversion.c:3157:21: warning: ‘__pyx_pybuffernd_dst_hours.diminfo[0].strides’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 3157 |   __Pyx_LocalBuf_ND __pyx_pybuffernd_dst_hours;
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~
pandas/_libs/tslibs/tzconversion.c:3149:21: warning: ‘__pyx_pybuffernd_ambiguous_array.diminfo[0].strides’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 3149 |   __Pyx_LocalBuf_ND __pyx_pybuffernd_ambiguous_array;

```