[Fix] Fix Segmenter-l readme

[linfangjian01]

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Motivation

Fix Segmenter-l readme

#1660

[codecov]

Codecov Report

Merging #1695 (d446006) into master (5ecf45d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1695   +/-   ##
=======================================
  Coverage   90.24%   90.24%           
=======================================
  Files         142      142           
  Lines        8486     8486           
  Branches     1432     1432           
=======================================
  Hits         7658     7658           
  Misses        588      588           
  Partials      240      240           

Flag	Coverage Δ
unittests	90.24% <ø> (ø)

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Impacted Files	Coverage Δ
mmseg/models/decode_heads/segformer_head.py	100.00% <0.00%> (ø)

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[MeowZheng]

please double-check the memory and fps