Fixed typos in schemview.py functions: delete_enum(), delete_slot(), delete_subset()

[puja-trivedi]

When using the functions delete_enum, delete_slot, and delete_subset I was getting these errors:

1. AttributeError: 'SchemaDefinition' object has no attribute 'enumes'.
   Which traces back to line 1663, in delete_enum: del self.schema.enumes[enum_name]

2. AttributeError: 'SchemaDefinition' object has no attribute 'slotes'.
Which traces back to line 1655, in delete_slot: del self.schema.slotes[slot_name]

3. AttributeError: 'SchemaDefinition' object has no attribute 'subsetes'.
   Which traces back to line 1679, in delete_subset: del self.schema.subsetes[subset_name]

When I change enumes to enums, slotes to slots, and subsetes to subsets the functions seem to work as expected.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (51d2fce) 62.80% compared to head (a959a20) 62.90%.
Report is 5 commits behind head on main.

Files	Patch %	Lines
linkml_runtime/utils/schemaview.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #301      +/-   ##
==========================================
+ Coverage   62.80%   62.90%   +0.10%     
==========================================
  Files          61       62       +1     
  Lines        8506     8529      +23     
  Branches     2239     2239              
==========================================
+ Hits         5342     5365      +23     
- Misses       2553     2554       +1     
+ Partials      611      610       -1     

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