Shift issue numbers in strings like issue([0-9]+), closes #7235

n -> n + 3099, see #7235

Remaining stuff:
$ grep -R 'issue[0-9]' [^.]*|grep -v '^sympy/mpmath/'|grep -v 'bugs.python.org/issue'
sympy/concrete/tests/test_sums_products.py:def test_evalf_fast_series_issue998():
sympy/integrals/tests/test_integrals.py:# issue1012

First was introduced in a945bc6
Second - in 98b4fc9