fix(http): Replace flush() with clear() in HTTPClient

[me-no-dev]

Following deprecation of flush()

[github-actions]

	Warnings
⚠️	The Pull Request description looks very brief, please check if more details can be added.

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Generated by 🚫 dangerJS against 175a017

[github-actions]

Memory usage test (comparing PR against master branch)

The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.

Memory	FLASH [bytes]		FLASH [%]		RAM [bytes]		RAM [%]
Target	DEC	INC	DEC	INC	DEC	INC	DEC	INC
ESP32S3	💚 -4	0	0.00	0.00	0	0	0.00	0.00
ESP32S2	💚 -4	0	0.00	0.00	0	0	0.00	0.00
ESP32C3	💚 -2	0	0.00	0.00	0	0	0.00	0.00
ESP32C6	💚 -2	0	0.00	0.00	0	0	0.00	0.00
ESP32	💚 -4	0	0.00	0.00	0	0	0.00	0.00

Click to expand the detailed deltas report [usage change in BYTES]

Target	ESP32S3		ESP32S2		ESP32C3		ESP32C6		ESP32
Example	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM
HTTPClient/examples/Authorization	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0
HTTPClient/examples/BasicHttpClient	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0
HTTPClient/examples/BasicHttpsClient	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0
HTTPClient/examples/HTTPClientEnterprise	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0
HTTPClient/examples/ReuseConnection	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0
HTTPClient/examples/StreamHttpClient	💚 -4	0	💚 -4	0	💚 -2	0	💚 -2	0	💚 -4	0

[github-actions]

Test Results

 56 files   56 suites   4m 51s ⏱️
 21 tests  21 ✅ 0 💤 0 ❌
135 runs  135 ✅ 0 💤 0 ❌

Results for commit 175a017.

♻️ This comment has been updated with latest results.