Update Base64SecretPatternFactory.java

[AbhinavJha1023]

Replaced loops with Streams: Improved readability and performance.
Used collect(Collectors.toSet()): Eliminates duplicates.
Optimized removeTrailingEquals: Uses charAt check instead of multiple conditions.
Encapsulation: Marked helper methods as private for better structure.

Testing done

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[jtnord]

the code does not compile.

[AbhinavJha1023]

the code does not compile.

Let me check this once again