Fix issues in number_line.py that changes in decimal_number_config["font_size"] get rewritten by number_config

[AStarySky]

Fix the issue that changes in decimal_number_config["font_size"] get rewritten by number_config

Motivation

When working with NumberLine in manim v1.7.2, I found that the decimal number label's size doesn't change with different font_size setting.

Proposed changes

Swaping the position of self.decimal_number_config and number_config in merge_dicts_recursively.
(Which gives self.decimal_number_config a higher priority, fixing the issue.)

Test

Code:

class BugDemo(Scene):
    def construct(self):
        NumberLines = VGroup(
            NumberLine(decimal_number_config=dict(num_decimal_places=0, font_size=48), include_numbers=True),
            NumberLine(decimal_number_config=dict(num_decimal_places=0, font_size=36), include_numbers=True),
            NumberLine(decimal_number_config=dict(num_decimal_places=0, font_size=24), include_numbers=True),
            NumberLine(decimal_number_config=dict(num_decimal_places=0, font_size=12), include_numbers=True)
        ).arrange(DOWN)

        self.add(NumberLines)

Result:

Before the change:

After the change: