const_string_encryption: Fix problem where static constructor not correctly found

[techee]

The current code expects that static constructors are declared as:

.method static constructor ()V

However, static constructors in smali files may contain the "public" keyword
so the static constructor has the form:

.method public static constructor ()V

The current code doesn't find such constructors and inserts another
static constructor to the code instead so there are 2 static constructors.
Smali seems to use only the first declared constructor (with the string
initializers) and ignores the second one with the original initialization
code which leads to uninitialized static members.

This patch simply relaxes the check of static constructors so there
can be an arbitrary string (including empty string) between ".method"
and "static".

[codecov]

Codecov Report

Merging #98 (31ee0f9) into master (8637197) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #98   +/-   ##
=======================================
  Coverage   77.57%   77.57%           
=======================================
  Files          49       49           
  Lines        2453     2453           
  Branches      486      486           
=======================================
  Hits         1903     1903           
  Misses        422      422           
  Partials      128      128           

Impacted Files	Coverage Δ
...const_string_encryption/const_string_encryption.py	85.29% <100.00%> (ø)

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[ClaudiuGeorgiu]

Thanks @techee!