Allow SymbolicIntegrationMaxima 0.3 in the qa test environment

[s-celles]

The qa group of the SymbolicIntegrationMaxima workflow fails before it runs a single
check:

ERROR: LoadError: empty intersection between SymbolicIntegrationMaxima@0.3.0 and project compatibility 0.2

lib/SymbolicIntegrationMaxima/test/runtests.jl activates test/qa and Pkg.develops the
local package into it, but test/qa/Project.toml still bounds the package under test at
"0.2" while #143 released it as 0.3.0.

This has failed on main since that release (run 35223647524), and every pull request that
merges current main inherits the two red qa jobs, which is how I ran into it on #136.

Widened to "0.2, 0.3", the same form #144 used for docs/Project.toml. The sibling bound
SymbolicIntegration = "3" is unaffected because it is a major-version bound; consider
whether this one should track major versions too, so it stops breaking on every 0.x release.

Verification

Running the exact sequence from runtests.jl, on Julia 1.13.0:

Pkg.activate("lib/SymbolicIntegrationMaxima/test/qa")
Pkg.develop([PackageSpec(path = pwd()), PackageSpec(path = "lib/SymbolicIntegrationMaxima")])

• before: empty intersection between SymbolicIntegrationMaxima@0.3.0 and project compatibility 0.2
• after: resolves, develop OK

Assisted by: AI

CI

35 checks pass, 0 fail, on a813e81 — including the 11 qa jobs this pull request repairs
and all 11 difficult jobs.

An earlier run of the identical change reported 4 failures: Julia pre - ubuntu easy,
Julia 1 - macos difficult, Julia 1.10 - windows difficult and Julia 1 - ubuntu qa. All
four concluded failure while every one of their steps reported success or skipped, so
no step had failed — the signature of an infrastructure failure rather than a result. That is
also what the scatter implied: this branch only widens a [compat] bound inside a test
environment's Project.toml, which cannot reach a difficult job on macOS. Merging current
main re-ran the matrix on the same one-line change and it came back 35/0.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.19%. Comparing base (8647f0d) to head (a813e81).
⚠️ Report is 29 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
+ Coverage   50.98%   51.19%   +0.21%     
==========================================
  Files          23       23              
  Lines        4309     4213      -96     
==========================================
- Hits         2197     2157      -40     
+ Misses       2112     2056      -56     

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