Effect GetFrame(): Use std::make_shared

[ferdnyc]

This PR tweaks the GetFrame(int64_t frame_number) overload in each effect from:

std::shared_ptr<openshot::Frame> GetFrame(int64_t frame_number) override {
    return GetFrame(std::shared_ptr<Frame> (new Frame()), frame_number);
}

to:

std::shared_ptr<openshot::Frame> GetFrame(int64_t frame_number) override {
    return GetFrame(std::make_shared<openshot::Frame>(), frame_number);
}

In accordance with #556, which did the same for other instances of shared-pointer creation. Extended rationale there.

[codecov]

Codecov Report

Merging #621 (57678ac) into develop (3b73425) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff            @@
##           develop     #621   +/-   ##
========================================
  Coverage    52.54%   52.54%           
========================================
  Files          129      129           
  Lines        10827    10827           
========================================
  Hits          5689     5689           
  Misses        5138     5138           

Impacted Files	Coverage Δ
src/effects/Bars.h	0.00% <0.00%> (ø)
src/effects/Blur.h	50.00% <0.00%> (ø)
src/effects/Brightness.h	0.00% <0.00%> (ø)
src/effects/Caption.h	0.00% <0.00%> (ø)
src/effects/ChromaKey.h	0.00% <0.00%> (ø)
src/effects/ColorShift.h	0.00% <0.00%> (ø)
src/effects/Crop.h	0.00% <0.00%> (ø)
src/effects/Deinterlace.h	0.00% <0.00%> (ø)
src/effects/Hue.h	0.00% <0.00%> (ø)
src/effects/Mask.h	0.00% <0.00%> (ø)
... and 5 more

---

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[jonoomph]

LGTM!

[github-actions]

Merge conflicts have been detected on this PR, please resolve.

[ferdnyc]

Conflicts resolved, merging.