[bugfix]修改了modules/utils.py中`initial_parameter()`函数的bug

[hy-struggle]

Description： 修改了modules/utils.py中initial_parameter()函数的bug

Main reason: 函数默认情况下使用init.xavier_normal_()初始化，但例如BatchNorm和LayerNorm这样的参数维度为1的层是不能使用这种初始化的。

报错为ValueError: Fan in and fan out can not be computed for tensor with less than 2 dimensions。

• [x] The PR title starts with [$CATEGORY] (例如[bugfix]修复bug，[new]添加新功能，[test]修改测试，[rm]删除旧代码)
• [x] Changes are complete (i.e. I finished coding on this PR) 修改完成才提PR
• [x] All changes have test coverage 修改的部分顺利通过测试。对于fastnlp/fastnlp/的修改，测试代码必须提供在fastnlp/test/。
• [x] Code is well-documented 注释写好，API文档会从注释中抽取
• [x] To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change 修改导致例子或tutorial有变化，请找核心开发人员

Changes: 逐项描述修改的内容

• 当参数维度为1时使用init.normal_()初始化。

Mention: 找人review你的PR

@xpqiu

[codecov-commenter]

Codecov Report

Merging #300 into master will decrease coverage by 0.11%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #300      +/-   ##
==========================================
- Coverage   78.57%   78.45%   -0.12%     
==========================================
  Files          95       95              
  Lines       12569    12571       +2     
==========================================
- Hits         9876     9863      -13     
- Misses       2693     2708      +15     

Impacted Files	Coverage Δ
fastNLP/modules/utils.py	85.71% <66.66%> (-0.96%)	:arrow_down:
fastNLP/core/callback.py	71.00% <0.00%> (-1.73%)	:arrow_down:
fastNLP/modules/generator/seq2seq_generator.py	75.61% <0.00%> (-1.24%)	:arrow_down:

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