Remove unnecessary namespace qualifications

[devmotion]

It seems there are quite a few examples of unnecessary namespace qualifications in DynamicPPL. This PR fixes a few of them.

[github-actions]

Pull Request Test Coverage Report for Build 5706550847

• 9 of 19 (47.37%) changed or added relevant lines in 8 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 75.47%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/model_utils.jl	0	2	0.0%
src/simple_varinfo.jl	0	2	0.0%
src/test_utils.jl	0	6	0.0%

Totals
Change from base Build 5695265951:	0.0%
Covered Lines:	2086
Relevant Lines:	2764

---

💛 - Coveralls

[codecov]

Codecov Report

Patch coverage: 47.36% and no project coverage change.

Comparison is base (2a1019b) 75.47% compared to head (0deb12e) 75.47%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #508   +/-   ##
=======================================
  Coverage   75.47%   75.47%           
=======================================
  Files          23       23           
  Lines        2764     2764           
=======================================
  Hits         2086     2086           
  Misses        678      678           

Files Changed	Coverage Δ
src/model_utils.jl	19.64% <0.00%> (ø)
src/simple_varinfo.jl	67.77% <0.00%> (ø)
src/test_utils.jl	84.65% <0.00%> (ø)
src/model.jl	88.34% <100.00%> (ø)
src/prob_macro.jl	84.67% <100.00%> (ø)
src/submodel_macro.jl	94.28% <100.00%> (ø)
src/transforming.jl	100.00% <100.00%> (ø)
src/utils.jl	76.95% <100.00%> (ø)

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[torfjelde]

Dopey:)