docs(examples): drop duplicated 'with' in sequence-length help strings

[simpleqt]

16 example scripts had --max_sequence_length help text reading "Maximum sequence length to use with with the T5 text encoder" (one uses the Gemma variant). The duplication surfaces in --help output. Mechanical one-word-per-file fix:

examples/controlnet/train_controlnet_sd3.py
examples/advanced_diffusion_training/train_dreambooth_lora_flux_advanced.py
examples/dreambooth/train_dreambooth_lora_flux.py (+flux2 variants)
examples/research_projects/sana/train_sana_sprint_diffusers.py
examples/research_projects/sd3_lora_colab/train_dreambooth_lora_sd3_miniature.py

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[github-actions]

Hi @simpleqt, thanks for the PR! It does not appear to link an issue it fixes. If this PR addresses an existing issue, please add a closing keyword (e.g. Fixes #1234) to the PR description so the issue is linked. See the contribution guide for more details. If this PR intentionally does not fix a tracked issue, a maintainer can add the no-issue-needed label to silence this reminder.

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[simpleqt]

Closing — pooled into #14715 combined docs PR to reduce review overhead. All fixes are preserved in the combined branch.

[simpleqt]

Correction: my closing comment pointed to #14715 — that number was wrong. The live pooled PR is #14757 (all fixes preserved there, now rebased onto current main).