`maths/binary_exponentiation_2.py` needs to be renamed

[tianyizheng02]

Repository commit

ef8df1451b7e9296cd3706cbfd0900f33acc4bb9

Python version (python --version)

Python 3.11.5

Dependencies version (pip freeze)

Dependency versions

``` beautifulsoup4==4.12.2 black==23.3.0 bs4==0.0.1 certifi==2023.5.7 cffi==1.15.1 cfgv==3.3.1 charset-normalizer==3.1.0 click==8.1.3 contourpy==1.1.0 cryptography==41.0.1 cycler==0.11.0 dill==0.3.6 distlib==0.3.6 fake-useragent==1.2.1 filelock==3.12.2 fonttools==4.40.0 identify==2.5.24 idna==3.4 joblib==1.3.1 kiwisolver==1.4.4 lxml-stubs==0.4.0 matplotlib==3.7.1 mpmath==1.3.0 mypy==1.4.0 mypy-extensions==1.0.0 networkx==3.1 nodeenv==1.8.0 ntlm-auth==1.5.0 numpy==1.26.0 packaging==23.1 pandas==2.0.3 pandas-stubs==2.1.1.230928 pathspec==0.11.1 pbr==5.11.1 Pillow==9.5.0 pip==23.2.1 platformdirs==3.8.0 ply==3.11 pre-commit==3.3.3 projectq==0.8.0 psutil==5.9.5 pycparser==2.21 pyparsing==3.1.0 python-dateutil==2.8.2 pytz==2023.3 PyYAML==6.0 qiskit==0.43.1 qiskit-aer==0.12.0 qiskit-ibmq-provider==0.20.2 qiskit-terra==0.24.1 requests==2.31.0 requests-ntlm==1.1.0 ruff==0.0.275 rustworkx==0.13.0 scikit-learn==1.2.2 scipy==1.10.1 seaborn==0.12.2 setuptools==68.0.0 six==1.16.0 soupsieve==2.4.1 stevedore==5.1.0 symengine==0.9.2 sympy==1.12 threadpoolctl==3.1.0 types-beautifulsoup4==4.12.0.6 types-html5lib==1.1.11.15 types-Pillow==10.0.0.3 types-pytz==2023.3.1.1 types-requests==2.31.0.1 types-urllib3==1.26.25.13 typing_extensions==4.6.3 tzdata==2023.3 urllib3==2.0.3 virtualenv==20.23.1 websocket-client==1.6.1 websockets==11.0.3 wheel==0.40.0 ```

Expected behavior

The file calculates exponentiation, a ** b.

Actual behavior

The file calculates multiplication, a * b.

>>> import maths.binary_exponentiation_2 as binexp
>>> binexp.b_expo(2, 3)
6

This file should be renamed to binary_multiplication.py. Also, we need doctests in this file so that basic errors like this can be caught.

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[AasheeshLikePanner]

Hi, I created a PR Can you please check it.

[AasheeshLikePanner]

Can you please check this new one PR

[piyush-poddar]

I have raised PR, please review it.