fix incorrect end-of-routine comment in dgemmtr

[nakatamaho]

Summary

This PR fixes an incorrect trailing comment in BLAS/SRC/dgemmtr.f.

-*     End of SGEMM
+*     End of DGEMMTR

Details

The routine body is unchanged. This patch only corrects the end-of-routine comment so that it matches the actual subroutine name.

Why this matters

Although this does not affect functionality, keeping routine names accurate in comments improves source readability and avoids confusion when browsing or reviewing the BLAS sources.

[langou]

This is an issue. Feel encouraged to provide a PR to fix it.