AnchorText - fix metadata

[RobertSamoilescu]

Currently, all parameters, correct or incorrect (misspelled), are included in the metadata.

alibi/alibi/explainers/anchor_text.py

Line 1229 in 390a255

self.meta['params'].update(**all_opts)

The valid parameters are stored in self.perturb_opts, which is set along with all_opts in:

alibi/alibi/explainers/anchor_text.py

Lines 1220 to 1222 in 390a255

	# validate kwargs
	self.perturb_opts, all_opts = self._validate_kwargs(sampling_strategy=sampling_strategy, nlp=nlp,
	language_model=language_model, **kwargs)

This should be an easy fix. Get rid of all_opts and update self.meta['params'] with self.peturb_opts.