Fix metadata iteration bug in FeatherPulsar class

[Wang-weiYu]

This PR fixes a bug in metadata iteration in save_feather function of class FeatherPulsar.

The original code:

meta = {}
for attr in Pulsar.metadata:
    if hasattr(self, attr):
        meta[attr] = Pulsar.to_list(getattr(self, attr))
    else:
        print(f"Pulsar.save_feather: cannot find {attr} in Pulsar {self.name}.")

was changed to

meta = {}
for attr in FeatherPulsar.metadata:
    if hasattr(self, attr):
        meta[attr] = FeatherPulsar.to_list(getattr(self, attr))
    else:
        print(f"FeatherPulsar.save_feather: cannot find {attr} in Pulsar {self.name}.")

The message in read_feather function:

print(f"Pulsar.read_feather: cannot find {attr} in feather file {filename}.")

was also changed to

print(f"FeatherPulsar.read_feather: cannot find {attr} in feather file {filename}.")

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 71.55%. Comparing base (dfe99d1) to head (a62c100).
Report is 19 commits behind head on dev.

Files with missing lines	Patch %	Lines
enterprise/pulsar.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #414      +/-   ##
==========================================
+ Coverage   71.52%   71.55%   +0.03%     
==========================================
  Files          13       13              
  Lines        3245     3245              
==========================================
+ Hits         2321     2322       +1     
+ Misses        924      923       -1     

Files with missing lines	Coverage Δ
enterprise/pulsar.py	28.62% <0.00%> (ø)

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[vhaasteren]

Code not covered was a pre-existing non-coverage from earlier. I'll approve and merge the PR, this was an obvious bug.