Updating the JsonObject method from getAsString() to toString()

[chitara-01]

Summary (Short summary of what is being done) :

Updating the JsonObject method from getAsString() to toString()

Description (Describe in detail the fix made) :

The DEID pipeline was failing on JSONL files when it had nested structure.

Pipeline uses getAsString() method call on JsonObject which throws exception with non-primitive data (nested structure in this case). Replacing getAsString() with toString() works. Please refer to [this](https://stackoverflow.com/questions/34120882/gson-jsonelement-getasstring-vs-jsonelement-tostring#:~:text=getAsString()%20is%20only%20defined,on%20all%20types%20of%20JsonElement%20.) stackoverflow link to understand the difference between the two.

Bug ID (if any) :

b/310247478

Public Documentation (if any) :

TESTED (Test Cases with scenario and description - must have 1 positive and 1 negative scenario) :

Tested DEID pipeline on the jsonl data file attached with the bug.

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (65fb1e4) 13.41% compared to head (01c6728) 13.41%.

Files	Patch %	Lines
...m/tokenization/json/ConvertJsonRecordToDLPRow.java	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #184 +/- ## ========================================= Coverage 13.41% 13.41% Complexity 67 67 ========================================= Files 53 53 Lines 2519 2519 Branches 213 213 ========================================= Hits 338 338 Misses 2161 2161 Partials 20 20 ```

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