Bug Report Template: Make example file valid

[tjlaboss]

This isn't really important, but the MCNP input file example given in the issue template for a bug report is:

1 1 20
         -1000  $ dollar comment
        imp:n,p=1 U=350 trcl=5

C surfaces
1000 SO 1

C data
C materials
C UO2 5 atpt enriched
m1        92235.80c           5 &
92238.80c          95

Obviously, this isn't a valid input file, nor does it need to be to for purposes of an issue template.

[tjlaboss]

Loosely related: #569.

[MicahGale]

Lol.