A bunch of typo fixes in comments and description strings

[abhisrkckl]

I am not adding a unit test because I have not changed any actual code. All the changes are in comments or description strings.

[codecov]

Codecov Report

Merging #1348 (93f223c) into master (60e8871) will not change coverage.
The diff coverage is 75.00%.

@@           Coverage Diff           @@
##           master    #1348   +/-   ##
=======================================
  Coverage   61.66%   61.66%           
=======================================
  Files          89       89           
  Lines       20233    20233           
  Branches     3646     3646           
=======================================
  Hits        12477    12477           
  Misses       6970     6970           
  Partials      786      786           

Impacted Files	Coverage Δ
src/pint/models/absolute_phase.py	96.00% <ø> (ø)
src/pint/models/binary_ell1.py	80.95% <ø> (ø)
src/pint/models/dispersion_model.py	90.58% <ø> (ø)
src/pint/models/jump.py	83.48% <ø> (ø)
src/pint/models/model_builder.py	93.50% <ø> (ø)
src/pint/models/parameter.py	81.72% <0.00%> (ø)
src/pint/models/piecewise.py	100.00% <ø> (ø)
src/pint/models/priors.py	95.45% <ø> (ø)
src/pint/models/pulsar_binary.py	76.24% <ø> (ø)
src/pint/models/spindown.py	86.02% <ø> (ø)
... and 11 more

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[dlakaplan]

is this ready to go?

[abhisrkckl]

I think so. There are no changes to the actual code in this PR.