graph : clean up t5 input builders (#18795)

graph : clean up t5 input builders (#18795)

* fix: Remove unnecessary `h` loops where `h` was only ever 0

Branch: CleanUpT5InputBuilders

Signed-off-by: Gabe Goodhart <redacted>
* fix: Remove unnecessary padding loop that is never hit anymore

The upper bound used to use GGML_PAD(n_tokens, GGML_KQ_MASK_PAD), but was
removed in https://github.com/ggml-org/llama.cpp/pull/17910 leaving the
loop dead.

Branch: CleanUpT5InputBuilders

Signed-off-by: Gabe Goodhart <redacted>
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Signed-off-by: Gabe Goodhart <redacted>