fix: remove usage of PHP 5.4+ shorthand bracket array declarations

[mehul0810]

Bug Report

User Story

As a user, I want to use export tools properly so that it runs without any issue.

Current Behavior

Currently, I've noticed that there are 2 lines of code under export tool shows usage of shorthand array declaration which was introduced in PHP 5.4 which won't support 5.3.

Expected Behavior

I expect to run the export tool properly in PHP 5.3

Bug Type

• This bug describes functionality that once worked in PHP 5.3 as expected in some versions earlier before commit 8fc6ee3.
• This bug describes functionality that never worked as expected.
• I am not sure whether this functionality ever worked as expected.

Possible Solution

• https://github.com/impress-org/give/blob/a90216c8ad9390d405a515cdfd1e625f2c7b6555/includes/admin/tools/export/class-batch-export-forms.php#L92
• https://github.com/impress-org/give/blob/a90216c8ad9390d405a515cdfd1e625f2c7b6555/includes/admin/tools/export/class-batch-export-forms.php#L114

Acceptance Criteria

• Use array() instead of [] for array declaration to support PHP 5.3
• Testing