Update system_update_8004 and taxonomy_update_8001 documentation typo 'indeces' to 'indices'

Yay spelling.

Same issue exists in taxonomy.install.
Can we catch them both here?

Thanks! That looks like it catches all of this particular word misspelling. I'll get it committed once the test bot line turns green.

There are actually two more misspellings of indices like this in 8.x. I committed the above patch, but could someone also patch:
core/modules/system/lib/Drupal/system/Tests/Form/CheckboxTest.php: // Only values that can be used for array indeces are supported for
core/includes/common.inc: * would. This means integer indeces are preserved just like string indeces are,

Thanks!

Assuming tests pass

From pre #6
grep -ir indeces core|sed 's/indeces/<strong>indeces<\/strong>/g'
core/modules/system/system.install: // According to the documentation of db_change_field(), indeces using the
core/modules/system/system.install: // field should be dropped first; if the contrib module created any indeces,
core/modules/system/lib/Drupal/system/Tests/Form/CheckboxTest.php: // Only values that can be used for array indeces are supported for
core/modules/taxonomy/taxonomy.install: // According to the documentation of db_change_field(), indeces using the
core/modules/taxonomy/taxonomy.install: // indeces, it is its responsibility to drop them in an update function
core/includes/common.inc: * would. This means integer indeces are preserved just like string indeces are,

I think that's all of them, assuming tests pass
Thanks Nick for saving face for me over #8 there :)

Patch passed (1894382-8-indeces-to-indices.patch)
Second file was an interdiff :) shouldn't have been tested.

Thanks! I'll get that committed shortly.

Commetted ;) and pushed to 8.x. Thanks!