Describe the bug

False-positives are returned for self-documenting f-strings.

To Reproduce

$ cat /tmp/test.py
a = 1
print(f"Hello world={a}")
$ vermin /tmp/test.py
Minimum required versions: 3.8
Incompatible versions:     2

Expected behavior

Expected the minimum required version for this code to be 3.6. A self-documenting f-string has the equals sign on the other side of the variable (i.e. {a=}).

Environment (please complete the following information):

• Vermin version 0.9.2

Thanks in advance!