Fix ALTER regression

[MauricioFauth]

Only parses the token if it is not a string.

• Fixes ALTER .. MODIFY ... ENUM failed! (Regression) #511
• Reverts Fix #478 - ALTER TABLE … MODIFY … ENUM('<reserved_keyword>') is being wrongly parsed #485
• Related to ALTER TABLE … MODIFY … ENUM('<reserved_keyword>') is being wrongly parsed. #478
• Related to Missing comma on ALTER TABLE with ENUM #234

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.01% ⚠️

Comparison is base (796b135) 97.02% compared to head (adfe314) 97.02%.
Report is 5 commits behind head on 5.8.x.

Additional details and impacted files

@@             Coverage Diff              @@
##              5.8.x     #512      +/-   ##
============================================
- Coverage     97.02%   97.02%   -0.01%     
- Complexity     2233     2236       +3     
============================================
  Files            69       69              
  Lines          5150     5144       -6     
============================================
- Hits           4997     4991       -6     
  Misses          153      153              

Files Changed	Coverage Δ
src/Components/AlterOperation.php	100.00% <100.00%> (ø)

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[williamdes]

This should go to 5.8.x and then do a fast release for it
What do you think?